Just found out that if you jump in water, and hit hide right as you hit. You can swim stealthed. Not only that, but when you come out of the water you can rest while stealthed, and also Pick up quest items without breaking stealth.
Kinda useless kinda neat. Works well as you're running from a ranger to dive in water-> stealth , lol
(This works on my barb, not sure about other classes)
:Edit: As i play around with this a little more I found out that If you break the stealth while in (or under) water , you get unlimited breathing and you can attack freely , Sprint and Rest in water O_O