An anchor alarm watches your position while you sleep and wakes you if the boat drags outside a safe circle. It is the cheapest insurance in boating, and your phone can do it. This guide compares the best anchor alarm apps in 2026, explains how drag detection actually works, and covers the setup details that decide whether the alarm fires in time or cries wolf all night.
For context: Marine OS is marina management software, and our route planner for boaters includes an anchor watch. The apps below are compared honestly, including where a dedicated app beats a browser.
- An anchor alarm is a GPS circle: set the drop point and a radius, and the app alerts when the boat leaves it.
- Aqua Map AnchorLink is the most capable: it mirrors the alarm across devices and sends remote alerts.
- Savvy Navvy and OpenCPN both include anchor watch alongside their navigation features.
- Set the radius from your scope plus GPS error, and mark the anchor at the moment you drop it.
- Phone-based alarms need power and signal to be useful all night, so plug the phone in.
#How an anchor alarm actually works
Every anchor alarm does the same thing: it records where the anchor went down, draws a circle around that point, and compares your live GPS position against the circle. If the boat crosses the line, it alarms. The quality differences are in the details: whether you can set the anchor position at the bow rather than where the phone sits, how it handles GPS jitter, whether the alert can reach a second device, and what happens when the phone locks.
#Aqua Map (AnchorLink)
Aqua Map has the most complete implementation. AnchorLink mirrors the anchor watch across your devices, so the alarm set on the phone in the cockpit can wake the tablet in your bunk, and it supports remote notifications when you are off the boat. If you anchor out regularly, this feature alone can justify the subscription.
#Savvy Navvy
Savvy Navvy includes an anchor alarm with customizable parameters inside its navigation app. It is convenient if you already use it for routing, though it is a paid app and the alarm is one feature among many rather than the specialty.
#OpenCPN anchor watch
OpenCPN is free, open-source chartplotter software with a built-in anchor watch. It runs on a laptop at the nav station, which actually helps here: laptops have bigger batteries and do not lock their screens the way phones do. The trade-off is setup effort and having a laptop aboard.
#Dedicated anchor alarm apps
Single-purpose apps such as Anchor Pro exist for one job and do it with deep settings: swing zones instead of plain circles, GPS averaging, loud custom alarm sounds, and battery-friendly modes. If you anchor out most nights, a dedicated app plus a navigation app is a sensible combination.
#Browser-based anchor watch
The Marine OS route planner includes an anchor watch in its Underway mode: set the alarm at your current position with a 10 to 300 meter radius, and the chart shows the watch circle, your drift distance, and sounds an alert with vibration if you leave it. It runs in the browser on any phone with nothing to install. The honest limitation: a browser alarm works while the tab is open and the screen is on, so it suits an anchor check with the phone plugged in, not a locked phone in a drawer. Dedicated apps handle background alerts better.
If you let out 40 meters of rode in 5 meters of water, your bow can swing roughly 40 meters from the anchor, and the phone GPS adds 5 to 15 meters of error. A radius tighter than scope plus GPS error guarantees false alarms; much looser and you drag a long way before it fires. Mark the anchor position at the moment you drop, then add margin.
Marine OS is marina management software, and our route planner for boaters now includes Underway mode with live GPS, an off-route alert, and an anchor watch, all in the browser. Plan the passage, and the same tool watches the hook at the end of it.
#Anchor tonight, plan tomorrow
An anchor alarm is one piece of the safety picture. Pair it with a float plan someone ashore can act on, and a tracking option so family can see where you are. For the planning side, see the best marine route planner apps.
Plan a route, then stand anchor watch in the same tool
The Marine OS route planner suggests the sea route, tracks you underway, and includes an anchor watch with drift alerts in Underway mode.
#Frequently asked questions
Frequently asked questions
Pick an alarm, learn its quirks on a calm night, and make it a habit every time the hook goes down. For the rest of the toolkit, see the best marine route planner apps and how to plan a boat route.
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