I have a GoPro Black. I never considered it a still camera at all. It would be difficult to use the button as a shutter release, and you can't see how you are aiming it! The GoPro gets turned on when you start, and stays mounted on your head or chest or whatnot; you don't fiddle with it or pay any attention to it while doing your activity.
However, a GoPro would be nice to have. Used in that manner: you can find strap mounts a lot cheaper than the ones they sell, so much so that I bought a head and chest set figuring I could mod them or use for parts, to strap it however I want. On Kauaʻi they are advertised heavily.
Since he's not a photographer, and it's best not to distract the novice diver with more stuff to fiddle with, the "turn on and forget" thing sounds like a good fit.
Include the waterproof housing, memory chip, and strap mounts, so he'll be ready to go. Set it for 2.5K (or 4K in the newer ones) resolution, and in post you can crop out a high-def section that's composed and stabilied (with niche software that is appearing, or a careful hand in a normal NLE). But that's a conversation for the video stack exchange.
(I wish I had something like that when drift diving in Arrecifes de Cozumel National Park! I'd say get that, and share a link when you upload the footage. :) )
Update: another comment makes me consider the low light. As a novice he really should be below the chop as it's difficult to keep position until you get more than 30 feet down. For shallower than that, use snorkell and stay at the surface! FWIW in sunlight I have no trouble seeing at the (plain) Scuba depth limit, or even inside a wreck. That's another advantage of video is the low-light performance. But check that when shopping! Waterproof to 120 feet is fine but can it still get a picture?