Glad you agree. My thought is that pressing the button would warp Rush in to your location and he would form the Marine around you, then pressing it again would teleport him out and let gravity take over. Plus, if Jay makes Mega Man able to jump all the way to the surface, as he can in the Mega Man games and has been suggested on these forums, then Rush Coil would truly be completely useless underwater, so you wouldn't be losing anything at all. I thought it might be nicer to have the option to play without the Rush Marine. Mega Man's games never forced you to use it, after all (except maybe in some of the Game Boy games).