I have some minor suggestions I would like to pitch and 2 questions regarding game mechanics. For my suggestions I would love to see more variety in the burping sound effects, have a bunch of different burps that can play instead of just 1. Maybe the mermaid and shark can have 2 different 'pools' of sound effects, the sharks being far deeper and louder.
I think it would also be cool if the game got some ambient stomach sounds added in, more gurgles as the mermaid grows in size, and especially have noise during the shark digestion of the player. Right now it feels rather boring and anticlimactic, some good digestion sounds and burping would make me feel inclined to get eaten ;)
I saw a comment posted here suggesting bubble effects when the mermaid or shark burps, I really like this idea and would like to add on to it. Currently when either fish-person burps, their mouth is closed. To make it feel like a burp they should switch to the frame of animation where their mouth is open with bubbles/ripples coming out. I personally would love to see an animation of their mouths rippling from the force of the burp or maybe their eyes roll back/cheeks get red but I understand that making sprites/sprite sheets are very time consuming and difficult. That is also assuming that you are still able to get new assets from AdjectiveNounCombo.
As for my 2 questions, 1, what does the eel ability do exactly, I'm not finding much success with it and it feels rather janky, how did you intend for it to be used? 2, I would like to know your reasoning for removing horizontal movement of the mermaid, I cant tell if I prefer the new or old movement better but I would like to know your thought process.