Name: Mizu Shihai(loosely translated as "Water Control")
Ability: Unlike Haku's "Ice Release" Kekkei Genkai, which combines Wind based Chakra with Water Base Chakra to create Ice, Mizu Shihai takes Water and Lightning. The water is overwhelmingly present, and the lightning-based chakra is in small amounts. However, this combination boils down to a molecular level that interferes with the bonding of one water molecule to the next. Thus, water can be converted into ice as electricity causes the molecules to draw closer to each other until densely packed like ice. And also water can be turned into vapour by causing molecules to draw away from each other ... creating a sort of fog if there is enough water.
Apperance: The physical stages of bonded 2 hydrogen atoms and an oxygen atom. Ice, Water, Water Vapour. Tatsuyo can combine his Kekkei Genkai with his Suiton(Water Style) Ninjutsu and use Ice type attacks.(XD) For example, the Mizu no Yaiba(Sword of Water) can be shifted from the water stage into ice, thus making it a more powerful weapon that requires less chakra to maintain.
History: A kekkei genkai that had gone through history in obscurity. It was only a few generations ago that it began to develop into what it is today. As mentioned in the character bio/background/history, there are a lesser and a superior variation in this trait. The difference is the power of the electrical chakra, and how much can be produced. In lesser trait users, the amount of lightning type chakra is scarce and rarely produced ... thus they cannot use the ability often. In superior, lightning-type is always continuously produced until it reaches set amount thus allowing longer and near endless usage. Lesser traits are known to not even bother using their ability, and usually do not end up ninja. Superior traits can make it a chunnin and some can claw their way into Jonin.