Really enjoyable experience. I like the idea for the game and it's design. At first it is a bit hard to get around but you can kind of get used to it. It is definitely original and it fulfills it's ideas nicely. Moreover, the presentation is quite nice. I liked the atmosphere of being in an unfamiliar, underwater area, it worked well.
Though there are a couple things I have issues with. First of all, food/hp from enemies would often fall through the floor, which was quite annoying considering how hard it was to get to that in the first place. Grapple would have some minor issues with connecting to enemies, but I am sure it is an easy fix. Also even though the upgrades are cool and fulfill their purpose, none of them felt like a good alternative to grapple. It was the easiest and most efficient to just grapple enemies around and get health. I think it could be improved because as it stands upgrades feel more like just opening a new path, and not actual power up.
Also I like the idea for health in this game, the body getting longer and falling apart when you get hurt too much. I feel it could give way to some puzzles/gameplay ideas where for example you could move faster when you are smaller or you could navigate easier, or you could just fit into tighter spaces the less health you have. And then the opposite for being big, where it would give you advantage during the fights but would be cumbersome during the movement. I think you could really explore that further and it would add a lot of depth.
All in all, really solid entry and I think it could turn into a great game. Nice job!