This is a really fun entry with a lot of great quality of life polish! You've got a great tutorial and fast mode helps the game so much. I love the pixel art and the theming, an aquatic tower defense is charming. I really appreciated how the music dynamically changes when you hit the start button that's a great piece of polish. You seem to have a good difficulty curve as well. At one point I started slacking just to see how much I could get away with and in one particular round I ended up losing most of my health.
I think my only two pieces of feedback for you are I would consider incentivizing the player to alter the trash path into certain spots. The mechanic of moving the path is really cool and I would love to see it used more. I'd also potentially look into increasing the variety of the sound effects.
Amazing job!