Need help

[GoFish]

Koodos on the quality pics! I was thinking Chiton at first too but a few things kept standing out. It looks too transparent to be one, it looks like it has appendages at the rear making it more agile, and also may have a separate head and even legs?

The closest thing I could find is called a Sphaeroma Quoianum, a type of Isopod...

Try having a look at these, they may be your critter