SeymourGore
Flatulent Cherub
I like the idea of flags floating on the surface of the water. And what you said about "skimming" across the water and what is required for it to work.. that can all be rephrased by saying that skimming or sinking depends on the angle at which the player makes contact with the water.
Yar, that'd be an adequate way of describing it. Forgive Seymour for his rambling ways!
Now when underwater, I believe there should be increased resistance (as you mentioned), blurry AND not lower vision range, and - here's where I disagree with you - energy should be required to jet up underwater, perhaps even more than what is necessary out of the water.
Yar, valid argument. I don't know about necessarily utilizing more energy, mind you. The reason being that the combination of increased resistance + increased energy consumption might be too much, and would make underwater combate more tedious than interesting/fun. Though, for sure it's more realistic for the energy requirements to be increased due to the increased resistance.
The more I think about it, the more I like your suggestion of energy being consumed, versus the original idea of energy being limitless underwater.