Art
The color scheme looks really cool, but at the same time it leads to a lot of problems. Because basically everything is black, it's difficult to say where the dangerous objects are (like spikes, bomb shells) or determine whether some wall is a part of the foreground (so it's an obstacle) or a part of the background. Also, as for the style, basically all sprites have a different pixel ratio and that kept bugging me. You had a very pixelly background and hyper-detailed sharks or bombs.
Movement
The hitboxes were really trippy. If you just try swimming against a wall you see how much bigger your hitbox is than it should be. It was really problematic. The swimming was really odd. I felt as if I kept accelerating and decelerating when swimming. This gives you a bunch of problems, since it's a game that requires your moves to be precise.
Sound effects
I really enjoyed the sound effects. They did justice to the game's atmosphere. It was very cool. Though the game over screen had a pretty irritating sound effect that doesn't fit the rest at all. I would probably preffer if the mother whale made a big cry. This would've made the player feel bad, instead of irritated.
Mechanics
Maybe that's just me, but I feel like the sonar ability doesn't really seem to add a lot. All it currently does, is it forces you to slow down, even though you are already going really slowly. Maybe you could make it so normally you can already see, but when you turn on your ability you see more but go slower.
It's a really cool game. It's also surprisingly similar to my axolotl game! Good job!