Yet Another Anchor Alarm, or The Best One

How to read the table

Three things fall out of it.

The basics are table stakes — the differences start one row down. Every product here detects drag against a GPS position; that is not where anything is won or lost. The first real fork is whether the alarm makes a noise on the boat: the phone apps and most monitoring hubs do not — they push to a phone — and the chartplotter’s beeper, where the plotter has one at all, is too quiet to wake anyone below. The dedicated hardware boxes, Smartboatia among the hubs, and Galvanic Voice are the ones that actually sound off in the cabin, and most of them do it with a siren, where Galvanic Voice speaks in plain words.

Past the basics, the field thins fast. A few rivals read wind or depth off the bus, one or two watch the barometer or steer you back to the anchor — but none starts the watch on its own, folds the falling barometer into it, and then speaks the problem aloud, all in one box. And the alarm nobody remembered to arm never goes off at all. That is why the Galvanic Voice row holds up across the features that actually matter at anchor.

And the sticker price is not the price. The cheapest-looking hardware is usually the most expensive to run. The cellular boxes and monitoring hubs — Nautic Alert, the Digital Yacht router, Siren Marine and most of the rest — need their own SIM or data plan to reach you at all, on top of a subscription of up to about thirty dollars a month; Nautic Alert’s satellite reach and GOST’s airtime cost more again. A box that looks cheaper up front — Siren Marine’s is $299.99 — then charges $22 a month on the maker’s own published plan, another $792 over three years, and keeps charging, every month, for as long as you own the boat. Galvanic Voice is €950 ex-VAT, once: no subscription, no SIM, nothing to renew — bought, in fairness, by leaving out the cellular radio those subscriptions pay for, so our ashore alert rides the boat’s own internet connection.

The detailed explanation

Be precise about what an anchor alarm is for, because the job is narrower and harder than the length of the market suggests. An anchor alarm exists to do one thing: notice that the boat has moved off its anchor, and wake the crew in time to do something about it. Everything else — the map, the app, the logging — is decoration around that single function.

One honest caveat before the tour. Plenty of experienced sailors never set an anchor alarm at all — an oversized anchor, enough chain, set hard and dived on, and they sleep soundly. They are not wrong: good ground tackle, well set, is the foundation, and no alarm replaces it. But even heavy ground tackle has dragged in a full gale; the boat that drags at three in the morning is often a neighbour’s, not yours; and in a crowded anchorage, on poor holding, or when you are ashore, an alarm is cheap insurance for the night you cannot be sure. It is not a substitute for seamanship, or in a real gale for a human watch. This piece is for the times you want one — and for the honest question of which.

There are, broadly, six kinds of anchor alarm; we take them in turn.

1. Phone and tablet apps

This is the largest category by far, and the least fit for the one job that matters. Anchor Pro drops a GPS geofence around your position and alerts you by Telegram or email if the boat leaves it. Ankeralarm does the same to the metre and carries its own anchorage database. Anchor Sentry arms itself once the hook is down; AnchorClub resizes the safe circle as the boat settles; Anchor Zone Alarm alerts you if you drift out of a guard area you draw on the map with your finger. Aqua Map and savvy navvy fold the alarm into a fuller chart app, where Anchor Pro — which runs on Android as well as iOS — is a dedicated, chartless anchor watch: a position logger with email/IM and sound alarms driving an exclusion zone, and a day’s track rather than nautical charts. Hooked adds remote monitoring and filters unreliable GPS, though its off-boat alerts need a second device and a paid subscription. The most capable is PredictWind’s Anchor Alert: paired with the company’s DataHub it reads live wind and depth off the NMEA 2000 network and can fire an Apple Critical Alert that overrides a silenced phone — but the full version wants a paid Pro plan and the DataHub box. SailGrib shapes the guard zone as an editable multi-sided area rather than a flat circle. SEAiq does the geometry properly, estimating where the anchor actually lies from the GNSS antenna offset, the boat’s heading and the scope veered, and putting distance and bearing back to it in the status bar — though the alarm reaches only the iPad it runs on. One name is missing on purpose: the Navionics Boating app, contrary to what many owners assume, documents no anchor alarm — that is a chartplotter feature, not an app one. A determined minority skip the app store and build their own — an anchor-watch plug-in on OpenCPN, a Signal K server driving Home Assistant automations, or a Victron Cerbo GX or Raspberry Pi wired to the NMEA 2000 bus. It works, and in our own community it comes up more often than most of the commercial products here — but it is a project, not a product, and once the skipper is asleep it inherits the same weakness as every app: the alarm still has to wake a phone.

They are cheap, and they share one flaw that is fatal for a safety alarm: the alarm has to sound on a phone. That phone must be charged, awake, un-silenced, in the cabin, and audible — and it must win a fight it was never designed to win. Both iOS and Android throttle background apps to save battery; Ankeralarm’s own instructions ask you to relaunch the app and disable battery optimisation for exactly this reason. Apple’s Critical Alerts entitlement, which lets an alarm override silent mode and Do Not Disturb, is granted only sparingly — PredictWind’s Anchor Alert holds it; most do not. So a meaningful fraction of alerts never reach a sleeping owner, the subject of a longer piece on why smartphones make terrible alarm systems. The phone brings a second failure: its GPS is imprecise — good to a handful of metres on a clear day, worse below decks — so the alarm either cries wolf every time the boat sails around its rode, or you widen the radius until it is too slack to catch a real drag. Sailors report exactly this, over and over: false alarms, lost trust, the system switched off in the end. The problem is not the code; it is the device the code runs on, and it cannot be coded around — a phone is built to be interruptible all day and quiet at night, the opposite of what an anchor watch needs. Step back from the individual apps, though, because the objection is not really about any of them. It is about the device. A phone is not a safety instrument and was never built as one. It is engineered above all for battery life, which means the operating system is designed to put background applications to sleep, and your anchor alarm will be a background application on the night it matters. It cannot deliver an alert without a network, by design, and the anchorages worth worrying about are the remote ones. Its battery is a consumable that depends on somebody having remembered to charge it. And it is a personal device that other people and other apps compete for: one glance at your email at midnight, one notification silenced by reflex, one flat battery, and the thing you were relying on to let you sleep is simply not there. As the one thing that has to wake you before the boat is on the rocks, no phone app is good enough, and no amount of clever code fixes a device built to be quiet at night.

2. Chartplotter anchor modes

Most modern chartplotters carry a basic anchor drag alarm, but, contrary to what most sailors assume, far from all of them do, and it is worth knowing which before you count on it. On Garmin GPSMAP and echoMAP units, on the Raymarine Axiom range, and on Furuno NavNet, it is native and free: the plotter records the GNSS position as the anchor goes down and alarms if you drift past a set radius. But a large slice of the sailing market has no native anchor alarm at all. The mainstream Navico generation — the B&G Zeus 3, Zeus 3S and Vulcan, the Simrad NSS evo3S, the Lowrance HDS Live and Elite FS — ships without one. We read all six operator manuals: in the B&G books the word “anchor” appears only in the AIS target legends, and in the Simrad and Lowrance books only as trolling-motor position-hold and shallow-water anchor controls. Only their newest units, the B&G Zeus S and Zeus SR and the Simrad NSX, have added a dedicated Anchor Mode, and we found no anchor alarm documented for Raymarine’s entry-level Element. So “you already own one” is not a safe assumption — and where you do, it may be a plain fixed radius, or a subscription phone-app feature rather than a function of the plotter itself.

Two things hold it back as a night alarm. The first is volume: the internal beeper is not built to carry through a closed companionway to a bunk forward, which is why owners routinely wire in external buzzers and cabin repeaters. The second is power. To keep the anchor watch running, the whole plotter — screen, processor and all — has to stay lit through the night: roughly 9 to 23 amp-hours over a twelve-hour night, against a house bank you are already rationing at anchor. That is a real cost for a screen no one is watching, and the reason we wrote the price of a watt. The plotter anchor watch is fine while you are awake at the helm; it is a poor instrument for the sleeping hours it is meant to cover.

The software-defined navigation systems are the newest arrivals here. Orca, which runs on a tablet or its own Orca Display, has a real anchor watch, called Guard Mode: a shaped geofence you size to the anchorage, a two-stage alarm that first reddens the safety-zone boundary on the chart and then grows louder, and a push to your phone when you are off the boat, provided the boat has its own internet. But it is still a screen and a phone — a reddened boundary and a notification, not a voice that speaks the problem into the cabin.

3. Boat-monitoring hubs

The connected monitoring box: Siren Marine, Sensar Marine, Seanapps, Roam, Glomex ZigBoat, BRNKL, Skyhawk Oversea, Boat Command, Vanemar and France’s Yacht Sentinel. Most carry their own cellular link — Yacht Sentinel its own 3G/4G — and run a geofence you can press into anchor-watch service. Glomex ZigBoat is the exception: it is wireless and cloudless, and reaches you off the boat through the boat’s own internet — the gateway joins your Wi-Fi or Ethernet — or an optional 3G/4G dongle on your own SIM, which is also what adds SMS. These are real hardware — a box with its own GPS and sensors, watching bilge, battery, shore power and a geofence, and sending it all to your phone. Some draw a fraction of a watt, because a box whose only job is to wake a phone barely has to do anything — and that low draw is beside the point. Look at where the alarm actually sounds: for most of them the hub detects the drag, but the alert is a push notification or an SMS to your phone, and the sirens some of these systems do offer are wired accessories for smoke, flood and intrusion; in the material we read, none of them sounds for the geofence.

Two exceptions deserve naming, because they are the ones that answer this criticism. Germany’s Smartboatia puts an 85 dBA buzzer in the housing and states plainly that its anchor alarm “runs independently of your phone” — the one hub here that sounds the drag alert on the boat itself, at €999 including VAT, with its own barograph, its own SIM and an automatic logbook. Denmark’s Sailserver stays silent aboard, but its anchor watch alarms on wind speed and water depth as well as drift, which almost nothing else in this category attempts. Neither speaks, neither starts itself, and both read wind and depth from the boat’s own instruments rather than sensors of their own — but it would be dishonest to describe the category as uniformly phone-only when these two exist. For the rest, it holds: the category inherits the whole weakness of the phone apps and adds two costs of its own — the hardware, typically a few hundred to around a thousand euros, and a subscription of up to about thirty dollars a month (a couple are free). As an anchor alarm specifically, a monitoring hub detects the drag with a better sensor than a phone, but the alert still arrives on a phone.

4. Smart anchor buoys and seabed sensors

This category takes on the deepest problem in every position-based alarm: to a GPS fix, a boat swinging in an arc on its rode looks almost exactly like a boat that has begun to drag. Morphéis and Swiss Ocean Tech’s AnchorGuardian answer it by measuring the anchor itself. AnchorGuardian puts a sensor on the anchor and detects its movement directly, sub-metre and independent of GPS; Morphéis floats a buoy over the anchor and flags it if the anchor shifts more than a few metres, however the boat swings above. For an anchor that is genuinely dragging, it works — a different approach from ours: they measure the anchor, we model the boat.

But be precise about what a device watching only the anchor can and cannot see: it answers “has the anchor moved?”, not “is the boat still attached to it?” If the rode parts, a shackle fails, or the windlass clutch slips and pays out another twenty metres of chain, the anchor stays exactly where it was set while the boat moves off it. Morphéis, which by its own description monitors the anchor and not the boat, is blind to that case. (AnchorGuardian is the more elaborate of the two — its seabed module also reports its distance to the boat, so it tracks the boat-to-anchor relationship rather than the anchor alone.) The general point holds for anything built to watch the ground tackle: it can be blind to the boat leaving it. Because we guard the boat’s own position, we notice it leaving the swing circle whatever the cause — a dragging anchor, a parted chain, or scope that has run out. You are not, in the end, trying to keep the anchor in place; you are trying to keep the boat off the rocks, and those are not always the same event. Their other limits mirror that focus: single-purpose devices that sound an alarm rather than speak the problem aloud. Morphéis is deployed by hand each time; AnchorGuardian installs permanently between anchor and chain, paired with a hull transducer, so it descends with the anchor. Morphéis is listed at around €1,499 (incl. VAT); AnchorGuardian markets to any vessel with an anchor, from leisure boats up, and publishes no price — available on request.

5. Dedicated onboard alarm boxes

Standalone hardware that makes a real noise on the boat, on its own, with no phone in the loop. Nautic Alert is the closest thing here to what we do, and it makes the opposite choices to ours. It carries its own GPS and its own cellular-and-satellite radio — which buys bare-boat independence and mid-ocean reach, and, in the same breath, a security box you arm by hand, a roughly 95 dB siren tone instead of words, and a bill of around thirty dollars a month for the connection. It is a security-and-monitoring product rather than a sailing-safety one, which is a difference in purpose rather than a deficiency, and nothing we score here turns on it. We left the radio out on purpose: the alarm that matters is the one that speaks in the cabin, not the one that chases a phone across an ocean.

Maretron‘s N2KView is the one product in this whole review built on the same principle as ours: it reads the NMEA 2000 bus directly and sounds a real alarm on the boat — through an ALM100 annunciator wired into the network — instead of pushing to a phone. Its anchoring module watches the drop and shows distances to and from the anchor, and, alone here, it adds a BNWAS: the bridge watch-keeping alarm that checks the watchkeeper has not fallen asleep. But it is a platform, not a product. It wants a PC or a dedicated display, a USB100 or IPG100 gateway and a licence key, add-on sensors before it can watch wind or pressure, and a paid cloud plan to reach you ashore. It monitors the whole vessel superbly; it does not speak the problem, start itself, or steer you back over the anchor.

Vesper Cortex is the nearest thing on the market to a talking alarm: an NMEA 2000 hub with an AIS transponder and VHF built in, which computes swing from GPS and a heading sensor and speaks a fixed, canned phrase that escalates into a siren. It still waits for you to arm it, the phrase is canned rather than a description of what is actually wrong, and the ashore anchor watch sits behind a paid Cortex Monitor Premium plan. Vanemar sits below it, sending an app push and automated phone calls on its own Vanemar Connect subscription (from $14.9/mo), and Digital Yacht’s NavAlert reads GPS off the NMEA 2000 network and can text you, but only by relaying through a separate 4G router that carries the SIM. Digital Yacht’s newer AIT6000, launched in April 2026, folds an anchor-drift alarm together with CPA/TCPA collision warnings into a single NMEA 2000 AIS transponder that keeps computing them even with no chartplotter switched on — the closest thing here to our own AIS-and-anchor combination, though it makes no sound of its own (it drives an external sounder) and cannot reach you off the boat. Yacht Devices‘ YDAB-01 Alarm Button is the cheapest answer to the commonest complaint about plotter alarms — a $189 NMEA 2000 amplifier driving your own speaker below decks, with a drag alarm and a rarer second alarm for when the GPS fix itself goes bad; it takes position off the bus, sounds tones rather than words, and does nothing off the boat at all. Two more shout or speak in earnest. GOST‘s NAV-Tracker pairs a geofence and satellite tracking with a roughly 100 dB siren; GOST publishes no price on its own site, and dealers list the tracker from about $1,350 to $2,300 plus airtime. And Exocet Safety from Pixel sur Mer genuinely speaks, in plain language, aloud on the boat — so we are not the only voice at sea, and it would be dishonest to claim we were. Exocet is a nine-function offshore-racing safety hub, listed at €10,950 ex-VAT; its alerts reach you ashore only through a separately paid 4G or satellite connectivity package. Like every other product in this section, it waits for you to switch it on.

6. Smartwatches and wearables

The newest lane is the wrist. Garmin’s quatix marine smartwatch has a native anchor-drag alert of its own: the current quatix 8 finds satellites on the watch’s own GNSS, records the drop, and vibrates on your wrist if the boat drifts outside a radius you set. It marks the anchor, but gives you no distance or bearing back to it. On the Apple Watch it is a companion to a phone app — DragAlarm and others let you silence the alarm from the wrist, and Anchor! — since withdrawn from the App Store — could arm and snooze it from there too, though the watch is still running off the phone’s GPS.

A wrist buzz reaches the wearer directly, without crossing a cabin or fighting a silent switch — but a vibration you can sleep through is a poor wake next to a voice that says the problem out loud. And it reaches exactly one wrist: the person wearing it. It says nothing to the rest of the crew, nothing to anyone ashore, it runs down a watch battery you now have to remember to charge every night, and it leans on the watch’s own GPS or a paired plotter. It is a personal alarm, not a boat’s alarm — the phone problem, moved onto a smaller screen. (The “watch” in Vesper’s old WatchMate, incidentally, was not a wristwatch at all but an AIS transponder with an anchor alarm; it has since been discontinued, and its successor is the Cortex above.)

What the whole market has in common

Two facts run through all six categories. First, every one of these products waits to be armed. Some make arming easier — Anchor Sentry starts once the anchor is down, AnchorClub sizes the circle for you, and Nautic Alert rejects false alerts caused by weather and GPS noise — but none decides, on its own, that you have finished anchoring and begins to watch. The most common way an anchor alarm fails in the real world is not a technical fault; it is a tired skipper at the end of a long passage who simply forgot to set it. Second, when the alarm does fire, it delivers a signal, not information: a tone, a beep, a push, a siren. You are woken by an undifferentiated alert that tells you something is wrong and makes you get up, find the device, and work out what. At their best, they wake you to a question rather than an answer.

What Galvanic Voice does differently

It starts itself, and this is the whole point. You do not switch it on. You do not open an app, set a radius, or confirm anything. You drop the anchor, and the boat is watched. Galvanic Voice uses multi-sensor technology, reading the NMEA 2000 bus, to establish on its own whether the vessel is anchored, and it settles the question in exactly five minutes (patents pending). From that moment the watch is running.

It also tells anchoring apart from lying in a harbour berth, automatically, so the watch runs when you are genuinely at anchor. Where the two are hard to separate it errs toward treating you as anchored, on the view that an alert you did not need is a nuisance and a missed drag is not. When you motor off the next morning it releases the watch by itself and files the stay in the history.

This matters more than any other line in this review, because the commonest way an anchor alarm fails has nothing to do with technology. It is a tired skipper at the end of a long passage who simply forgets to set it. An alarm nobody armed does not go off. Every other system on this page waits to be switched on; ours has already started.

It understands the geometry. It does draw you a circle. The difference is how the circle is arrived at: rather than a radius you guess at sunset, it builds the most probable swing circle and the most probable anchor position from the conditions themselves, computing the catenary — the actual curve the chain takes given water depth, chain deployed and wind load — and updating it as the wind and the depth change. The reasoning is set out in the real chain reaction. And because it watches the boat, not the anchor, it catches a departure however it happens — not only an anchor that has moved.

It watches the conditions, not just the position. Most anchor alarms watch a single number — your distance from a dropped point. Galvanic Voice reads the same bus for wind, depth and barometric pressure and folds all three into the anchor watch, because those are the forces that actually move a boat at anchor. A rising or veering wind is what drags an anchor, so it feeds the live swing model and speaks up when a shift starts eating your swing room (“Wind direction changing. Check swing room”). A falling barometric trend is the earliest warning of all — the squall that will test your holding, announced before the wind has reached the anemometer. And it watches the depth under the keel, feeding it into the swing model, and it will alarm on depth at anchor if that is what the skipper wants — the anchor watch and the navigation watch each carry their own depth toggle, so you set the shoaling alarm you want for the night without inheriting the one you set for passage-making. The full reasoning is in the intelligent anchor alarm.

It speaks, in words, aloud, to the whole boat. When something is wrong it does not just beep. It says what is wrong, through a 20-watt exciter bonded to the glass face of the unit at over 90 dB SPL at one metre — far louder than a typical phone speaker. It is not the loudest device here; the dedicated sirens out-shout it on raw volume. But those decibels carry meaning rather than a tone: it names the problem in plain language, so you know from your bunk whether it is worth getting up. When it is time to recover the anchor it talks you back over it, giving relative bearing and distance until the anchor is directly below — and a buoy / compass screen guides you back to the boat from the dinghy or shore, bearing and distance in hand. We are not alone in giving you the numbers — Ankeralarm, Hooked, SEAiq and Maretron all put distance and bearing to the anchor on a screen — but we are alone in speaking them, which is the difference between a readout you must go and look at and an instruction you can follow with your hands on the windlass.

It remembers, and it watches the crew. Every anchorage is logged automatically — an anchor history you build without lifting a finger. It also watches where the crew are, and it reads the situation before deciding how loudly to react. A worn Galvanic Pulse bracelet that leaves the boat at anchor, in harbour or alongside is a benign event — somebody has stepped ashore or into the tender — so it is logged rather than shouted about. The identical event offshore at night is not benign, and it is raised as a full emergency, spoken aloud, loud enough to wake the whole boat within seconds, then repeated with relative bearing and distance to the casualty until the recovery is over. A man-overboard alarm that cannot tell those two apart is either useless at anchor or dangerous at sea. Two bracelets come as standard, six during the pre-order. And the anchor watch is one quarter of what the unit does: traffic, environment, vessel and crew — four spoken safety domains, situational awareness for the whole boat, in a single box that draws about 1.1 W, needs the boat’s own sensors live but not the power-hungry plotter, and asks no subscription.

The honest trade-offs

Fair is fair. Galvanic Voice reads its position, depth, wind and barometric pressure off the boat’s NMEA 2000 bus, so it needs a working backbone and those sensors powered; it is not a bare-boat standalone the way a self-contained GPS box is — though it does not need the thirsty plotter either. It has no cellular or satellite radio of its own: the ashore alert is an app push over the boat’s connection, which, like everyone else’s, depends on a phone to receive it. Its coastline database gives you navigation-zone awareness, not hazard avoidance; rocks and shoals are the chart’s job. And with no long-range radio, unlike a self-contained box, it cannot reach you out of phone range, mid-ocean. That was the deliberate trade: an alarm that speaks where the crew sleeps, rather than one that reaches a phone ashore.