Overall great game. I like the jet mechanic and the swimming is nice and smooth.
Couple suggestion that I have:
• I would make the controls less "floaty" as it is hard to control sometimes. Character gains a lot of momentum and its hard to stir him, especially in mid jump
• Make character not automatically fall from the ladder when reached its end, but only when jump button pressed
• Maybe the ability to shoot arrows while climbing ladders would be cool?