Been really enjoying Subnautica and it is generally remarkably bug free - but it has one glaring massive bug - if you leave the Seamoth mini-sub too close to geometry it can drift into/through it and become unreachable, if you leave it unattended. Happened to me in early access and it's happened to me in the most recent version of the game.

But there's a solution, I just used it, shown in the video below:
https://youtu.be/AWSOCXzTxxk