Thank you for playing!
The swordfish should definitely not be going through walls, I'll need to give them a talking to.
I agree that a grid based movement system would have been a better approach. I had concerns that the stages with open areas wouldn't work how I wanted if the player was stuck on a grid, but I think this was a mistake on my part. It would also have solved a lot of problems I had with the eel segments such as how the jellyfish interacts with them. Next time I'll know better!