This was really great! The static camera angles!!!! *Chefs Kiss*
I really liked the carrying of the mermaid part too, so great! I think the hallways were a little too difficult to navigate as they all looked the same, I don't think it needs to be maze like, I think it would be fine to add some details to act as landmarks or turn off the lights in some of the hallways, maybe a leaking roof or a window to the outside to really give the feeling like it was underwater.
I found the mermaid first and then the elevator. Then you have to go back to the mermaid to trigger the "hand" thing. That seemed kind of counter intuitive. Perhaps there is a crowbar or set of keys or a button to unlock her from the chair near that elevator and you press that first so that when you go back to the mermaid you can "rescue" her and only then take her to the elevator to escape.
I also really wanted a RUN button!
I really enjoyed this one, great job!