Questions, answered

An iPhone. The watch app needs an Apple Watch Ultra (any model), because it uses the Action button and the Ultra's depth sensor. You can also plan on a computer with the web app at app.getaspetto.com.

The 1–2 m surveys cover Dodman Point to Whitsand Bay in south-east Cornwall. Everywhere else you get EMODnet's map at about 115 m, which shows the shape of the ground but not individual reefs. We're adding more UK surveys; sign up for the beta and tell us where you dive.

No. It isn't certified or tested as a dive computer (EN 13319), it doesn't calculate decompression, and it isn't for scuba. It's a freediving and spearfishing log, planner and check-in tool.

To 6 m. Aspetto uses Apple's shallow-depth access, and below 6 m the reading isn't valid. Depths on the map can be deeper because they're charted depths, and they're labelled that way.

No. The maps are for planning where to look. Survey data can be old, close inshore the depths are estimates, and the tide model is good to about half a metre. Use proper charts for navigation.

The watch sounds an alarm and counts down for 20 seconds, then goes to SOS: it saves your position and shows a call button. If you've added emergency contacts, they get an email with your last position. Texts are coming. In the beta, alerts go only to your own email.

None of this can happen while you're underwater, and it can't bring help fast enough for a blackout. Always dive with a buddy.

No. Water Lock turns the touch screen off, so in the water everything works with the Digital Crown and the Action button: start, mark a spot, next spot, zoom, torch, "I'm OK" and end.

The watch logs dives and shows the seabed offline; the iPhone sends it the map tiles round you and your spots before you go. Check-ins with the server and SOS emails need the watch to have a connection when you're at the surface.

Only you. Your spots, dives and catches are never shown to other users, sold or used for advertising. You can use the app without an account (everything stays on your devices), or sign in to sync with your other devices and the web app. Full details in the privacy policy.

The beta is free. We'll say what the app costs well before it reaches the App Store, and beta testers will hear first.

Not yet. We're looking at both. Sign up for the beta and tick what you have, so we know who's asking.

Aspetto is made in Cornwall by a spearfisher who wanted to see the ground before getting in. "Aspetto" is Italian for the technique of waiting still on the bottom for the fish to come to you. Say hello at hello@getaspetto.com.