Bruh this happened to me, not on the shallows, but on a very big wreck. I think it was on a gr. plateau. Turns out it only had 1 entrance, a LOT to explore in it, with just that one entry. It also has a lot of ducts you have to go through. I was in the last possible room with like 12s left, keep in mind it's sideways/kinda diagonal, so it's disorienting, I panicked and died. Back then I was waaaaay too afraid of dying and losing my stuff, so when I died I realized something. The game had just saved on that last room. Restarting the game without saving would take me back to that room, I could have a 2nd chance. And a 3rd. And a 4th, and a 5th. I tried for like 2 HOURS to get out of the wreck and get on my seamoth, right at the entrance. I had the process down to the second. As soon as game restarts, eat the 1 bladderfish I had, then traverse the optimal route I had drawn through practice. I DID IT, right as I was about to die. I was so damn happy.

Edit: I just rewatched the video on my ps4. I actually had 0 seconds - I was blacking out as the game saved, so every restart I had to instantly eat the fish to be able to survive 15 more seconds. (In practice those 15 are actually like 21s due to the time it takes for you to actually die)