I do know what you mean. Clineschmidt's Blade. The underwater tunnels are pretty confusing. I use the central circular place to get air, check my direction on the compass, and take the middle one then the bottom one. one leads to the correct room, one leads to the escape well from the correct room.
The only other tunnel is back to where you began.
YES, it gets confusing. I've played the game more than a hundred times, and I still get lost occasionally in this spot.
(On the plus side, every once in a while, I'd get to see the schools of fish, but they aren't always there.)
"Great Gulgren's Sack!"