really great potential if the game is fleshed out and polished. some cutscenes, dialogue, interactions, better graphics, better controls, animations, etc. But the overall concept and character design seem amazing! cant wait for a finished product (although I absolutely can and ill wait years if I have too.)
also, this would be a really fun console horror game. maybe even in VR? although controls would need a rework for that. maybe you would use actual hand motions in VR to move and then you can have mirrors around the map to look at yourself.
I also noticed the excessive bleeding so maybe some progressive bodily changes like your body and stitching and open wounds start falling apart or get worse overtime like your becoming more zombie like? might be more aesthetically pleasing as the facility gets darker and you start swimming in deeper/darker waters.
maybe some more enemies could be other experiments or creatures suited for high pressure/deeper water sea creatures.
maybe a mini-boss or something that's a sea serpent?
Could these researches have a bigger goal entirely than just turning people into mermaids?
I would also love to learn more about our MC.
She's a silent protagonist who seems to not be very expressive (since she doesn't seem to be bothered very much by the fact she's missing half her body and is completely mutilated and bleeding with open wounds apart from her head hurting the one time.)
maybe she's on pain meds and they'll wear off very soon or maybe its just the shock and adrenaline getting her this far ATM. Who knows? ANY-ways, this is very interesting and I'm already in love with it. I can't wait to see the finished product and I hope the development goes well and that my constructive criticism helped!