Watch Ultra 4

The case is rated to 100 m (328 ft) under ISO 22810 and certified to EN13319 for recreational scuba to 40 m (131 ft), with a depth gauge accurate to a metre and a water temperature sensor. Those are real dive-computer credentials, not a marketing line, and they sit in a watch you were going to wear to breakfast anyway.

Read the next part before you cancel your Perdix order, though. Out of the box the Depth app gives you depth, water temperature and elapsed time, which is a gauge, not a computer. Everything a computer actually does, no-decompression limits, ascent rate, safety stops, a dive log, comes from Oceanic+, which is a separate app on a subscription: $79.99 a year in the US store, EUR 88.99 in the European one. Budget for it, or the watch is an expensive bottom timer. The App Store prices it by storefront rather than by what it does, so the same subscription runs to about a third of that on an Egyptian account, and if you dive one week a year the day pass at $4.99 is the honest way to buy it: seven days on a liveaboard comes to less than half the annual.

And 40 m is the ceiling for a reason: this is a recreational tool. No gas switching, no trimix, nothing to say to you if you go into deco. As a second computer on your other wrist, or as the one you take on a holiday where you dive four times, it is excellent. As the only computer on a dive that needs planning, it is not.

The 3000 nit display is the underrated part in the Red Sea. At 30 m on a bright day, with the sun straight down through clear water, most screens wash out and this one does not.