There’s a GoFundMe account set up.
Surprise Surprise
Yep.
From the pics, it doesn’t look like that deep of a dive but obviously this guy was underwater too long.
https://www.atlasobscura.com/places/the-underwater-room-at-the-manta-resort-tanzania
From what I saw, he shows the note, presses it against the glass, flips it over, presses that against the glass and then pulls the ring box from his pocket.
https://www.youtube.com/watch?v=TzFJuj6F23U