Thanks for the feedback, the controls are something I wanted to make more clear. It's easy to overlook their complexity/akwardness when you are the dev haha. If it helps theres a bar at the bottom left corner. It represents how much your submarine is currently filled with water which handles your vertical movement. To little water and you will receive a constant force to go up, too much water and you constantly receive force that sinks you. This is to mimick how a submarine works irl, but with no real in game tutorial/explanation (ran out of time) I think its impossible to guess.