Not saying you're wrong, but Mesmers don't usually hang out in the same places as Crashfish.

There's a big cave system underneath the northern hotspot, and there's an area in there that is absolutely lousy with Crashfish -- like 7 or 8 of them all clustered together. Maybe look for that. If there's nobody there, I'd say it's almost definitely a bug!

TL;DR: I think it was a loading error. I KNOW I searched a few of these caves before and crash fish are hard to miss; they aggro when you swim by them and explode. Next time I'll just build my own radio after a few minutes instead of trying to fix the broken one.

I was able to get a scanner room put together. I wrote the first post after saving and quitting, and today I loaded it up, and I stopped running around with the sea glide going into every cave I could find and manually hunting fish to not die. I had slapped a tube down 20 yards from the pod, built a radio in it, and started progressing the game. Even built the seamoth and realized I wouldn't be able to repair it until I found some cave sulfur. Acquired growbeds and plants. Found scanner room pieces to get the blueprint, and set it up immediately to look for sulfur. In the immediate vicinity of my pod, there were only two points. Off away to the northwest, there was a cluster of 4 or 5, and then there's a bunch of scattered ones to the south. I KNOW I searched the cave that was nearest before, so I think maybe there was an error when loading up the game. Crash fish were there this time. So were the eggs I noted previously (I didn't pick them up before.)

Standing in my scanner room and facing Lifepod 17, I'm facing WSW (A notch west from SW) and it's 569m away. Lifepod 3 is just one notch west of North on my compass. I'm further north than I had assumed at first, I must be pretty much in the midst of the safe shallows. I avoided going towards the Aurora because I thought I was further south, but that's were all the crash fish are on my map.

All in all, I think the next time I restart I will just build my own dang radio if I can't find a crash fish in the first ten minutes and save myself the grief.

At first I had to spend time finding crash fish/sulfur.
Finally in the kelp zone, near the games starting point there are quite a few caves, usually there are crash fish that come at you then go to their pod. I know you know that already, but my problem was only having 45 seconds of air at the start, so I didn't go far enough into the caves.

The first crash fish I found was after the first air upgrade. It came at me, took half my life, I didn't know they did that! Anyway I panicked, got lost in the cave and died anyway due to running out of air.

After that first encounter I knew where to look and what to expect so it was pretty easy.
A little or medium way in to caves in the kelp zone. There are lots. One in/near a thermal vent cave. Oh and if memory serves, the caves are not the really shallow ones, probably at least 30 meters down and more, then time needed to deal with the Bxxtxxxds and grab their sulfur. (Make a note of where the nest is - the second time I didn't note where it came from, swam around - and died of O2 hypoxia. So it wasn't in fact until after the first two times it became easy.