I'm about to release the Waterwalking spell tonight or tomorrow. I'm still doing some testing and it seems to work like a charm. I made the spell to last for 60 seconds and it can be recast at any time, when the player is on the surface of the water. Spell is going to be Alteration spell and I made it cost 110 magicka, depending on the player's skills, level and perks.
I have also made the spell like the one was in Oblivion. So, as long as the spell will last, the player can walk on the surface of water. So, no jumping to keep the player on the surface.