Wait, are we really calling 90 seconds a sudden wall when you had time to notice it happening? I've been in silty water my whole career and yeah, it gets dark fast, but zero viz at 60 feet with a pipe to follow is more annoying than dangerous. You had the pipe, you had the line, you just had to feel your way out. The guy who took four hours to find a lift bag, that sounds like a training issue more than anything else. If you're working bottom contact in soft silt, you should already be expecting this and have your hand on the structure before you kick. I'm not saying it's fun, but calling it a wall makes it sound like you weren't prepared for what happens in that environment every single day.

That automatic feeling around 150 is real. My tension changed too, but it was my thumb pressure more than the sewing itself. Once your hands stop second guessing, you start pulling consistent without even thinking about it. One thing that helped me was rechecking my thread pull on every fifth section, because the muscle memory can hide small slips that show up later in the rounding. Also don't toss those failed testers, I keep mine labeled with what went wrong and they're better than any guide when I hit a weird text block.