This is your standart 2D action-platformer! Oh wait... It's not. Well, be warned that this short free flash game is confusing and strange, and in the end, you may don't like it at all... or not.
That screenshot sure reminds me of Cave Story. Must be the style.
The underwater part certainly reminded me of Keen, with all the fish following me. But the level design is rather boring so there's where I stopped playing.