Cool concept, but mixed execution. I feel this is one of the games where the low resolution hurt it. The limited view (plus lack of ability to turn around) caused a lot of trial and error. It also took me a while to realise that you can hide from the fish by staying in the grass. Perhaps that could be mentioned in the instructions?
On the positive side, the concept of a crab walking around walls with only jumping/stopping to control yourself is neat. Once you get used to it, it's pretty fun. The overall art style is very charming - both the colour palette and the sprite work. The music is nice too. I like the addition of shells to collect for extra challenge, though I only got a few of them.
The end screen stopped before I could take a screenshot, but my favourite shell was the floppy disk.