Anchor Watch

Sleeping well at anchor

Anchor watch apps are a godsend on a modern cruising boat. We have three of them.

We are presently tucked into Kiwiriki Bay in the Port Fitzroy area of New Zealand’s Great Barrier Island. It’s a raging gale outside the protected confines of the harbour—gusts in the high 40-knot range. Inside where we are anchored, the rain pours down endlessly, and the wind swirls around.

PredictWind’s “Observations” page shows how nasty it is out there. Source: PredictWind.com

The anchor is set in mud just off of a knob of hillside with valleys to either side of us. This is proving to be a good spot so far. The wind is shifty, but lighter than further out in the bay.

In the bad old days, we’d take bearings off nearby prominent land features or navigation aids. We’d plot those bearings on a harbor chart or plotting sheet. We’d post an anchor watch and check those bearings once per watch. But it’s not the bad old days anymore. Today, we have apps.

We have three running right now: The crappy anchor alarm on our B&G Zeus 3S chart plotter; Anchor Pro, a long-time favorite, is running on the iPad; PredictWind’s new AnchorAlert is running on my iPhone.

L-R: B&G Chart Plotter, Anchor Pro, Anchor Alert

All three apps plot our shifting position as we slew around in the breeze. All of them will sound an alarm if we swing or drag outside the designated safe zone. Having them running allows us to snooze at night knowing we’ll get rousted up if we drag.

We did some testing for PredictWind last year and provided feedback on their app. It’s gotten very good now and has become our preferred anchor watch app. Its best feature is that it updates our position to the PredictWind cloud (via Starlink), which means we can keep an eye on the boat while ashore (assuming we have a cell signal).

Anchor Pro can notify you remotely of an alert as well, but it does it over email, which means you have to constantly check your email ashore.

The chart plotter has a simple alarm. It sounds if the boat drifts outside a designated range (in feet or meters). It doesn’t have a way to identify where the anchor was dropped and thus you can’t get a clear picture on how the boat is behaving at anchor. Why a modern chart plotter doesn’t have a better anchor alarm is a mystery.

Looks like one more day of this nasty weather, and then we can go sailing again.