Sailing

Man overboard alarm on every crew phone

At night, in a seaway, or with everyone busy on deck, someone can go over the side without anyone seeing. Crew Guard turns the phones your crew already carries into a man overboard alarm: if one goes silent, every other phone sounds the alarm within 30 seconds and points back to where it was last heard.

How it works

1. Join the crew. Everyone scans one QR code on the dock. No account, no internet.
2. Start the guard. The phones keep in touch over Bluetooth and Wi-Fi, with the screen off, from the time the boat gets under way.
3. Someone goes in. Their phone drops out of range or into the water. The others try to reconnect for 15 seconds, then show “Checking Dan…”. After 30 seconds, every phone sounds a full siren, over the lock screen and Do Not Disturb.

What the alarm screen shows

Who is missing, an arrow and distance to where their phone was last heard, and the coordinates, ready to read out in a Mayday call.

It doesn't need the phone to survive

The alarm comes from the other phones noticing that one has gone silent. A phone that sinks or dies in the water still triggers it.

Made for real boats

• Armed only under way (above about 2 knots). At anchor, a silent phone brings a soft warning, so a swim or a trip ashore doesn't wake everyone. Turn on Always armed if you want the full alarm at anchor too.
• Below deck still counts: every phone passes on what it heard, so a phone in the cabin is heard through the others.
• Switched off isn't overboard: a phone that's turned off or out of battery says goodbye first, and that brings a gentle warning, not a siren.

Compared with tag-based MOB systems

No tags to buy, charge or hand out, and no unit at the helm. Everyone aboard who carries a phone is covered, including guests and charter crew. Range is usually tens of metres and depends on the hull and conditions. On a boat that's enough: what matters is noticing that someone is gone.

What it isn't

Crew Guard doesn't call rescue services and isn't a certified MOB device. Keep wearing lifejackets and harnesses, and carry a PLB or AIS MOB beacon. Crew Guard is the fast first warning that tells the crew to act.

Read next: Man overboard: the first 60 seconds, a checklist for your crew. Also: paddling, hiking and mountaineering.