This was fun! I'm all for cetaceans taking back the ocean, and hope that recent events lead to humanity being more thoughtful about how we interact with and move through their spaces.

The game seems well-scoped for the jam, and I appreciated how the generated(?) levels' complexity mapped well against the available time across a number of runs.

I want to question the licence you've mentioned for the assets you've used - the Unsplash web page lists a licence that is not and has more restrictions than CC0. The base Unsplash licence is compatible with the jam, but it does not explicitly grant the right to relicence. 

As noted on the Creative Commons website:

You should only apply CC0 to your own work, unless you have the necessary rights to apply CC0 to another person’s work.

I enjoyed this a lot! Simple gameplay, but stunning pixel art! I also liked the wholesome concept of  mercilessly drowning people :D