I love the idea of a more exploratory space shooter, and the dual air and sea mechanic is a lot of fun. I think it still needs a bit of work, though. My biggest issue was that it was just too hard to distinguish where the walls that would kill you were. The backgrounds are beautiful, but they blend in way too much with the foreground walls, especially in the caves where one wrong move can kill you. Adding some sort of visual que to the surfaces that can kill you would go a long way.
Another suggestion I have would be a small mercy invincibility period after respawn. There were several times that I'd die, respawn, and then immediately die again because there was an enemy spawning or shooting near that area.