Hey no worries! I didn't take it as it being harsh or anything haha, just wanted to clarify that it was a bug and not a lack of time/over-scope thing.
There are 9 audio logs in total, so definitely more than 4! It's only necessary to go underwater for 3 of them though. It's a bit difficult to say how many underwater areas there are exactly, as a lot of it is all interconnected. There is one large research chamber that is only able to be reached by swimming, and that one in particular is where I imagine most people got lost and died, as there's one split where it's a dead-end to the left but the right goes to the research area. There's also one long interconnected underwater tunnel segment that is broken up into two areas where you can surface. It connects one of the research chambers you can get to without swimming all the way back to the main central chamber (where you can refill your glowsticks).
Again, no worries about your feedback, it's what the jam comments are for :) Besides, the level design is certainly far from perfect as I'm not really a level designer to begin with. I can completely see where some areas could feel very same-y, especially given the dark lighting. Thanks again for your feedback and playing the game!