I Like your game and fro 5h it is a wonderfull product that fels polished and has a nice intro with simple rules that you pick up quick. I would reduce the pumping effect ust a tiny bit, to make the experience a bit more flowy and less panicking, but i think that was your intention and as sutch, works rely well to build up tension. Mybe just start it soft with the watermeetre at 0.75 and remove the visual guide to get the tension from the fakt that you dont knwo how close to death you are.
Over all a wonderfull product for 5h! Keep Going!