Slipstream

When cast, this spell allows the caster to merge with any sized stream of running water. Basically, the caster become a part of the stream, allowing himself to be carried along with the current undetected by normal means. Needless to say, this is quite useful if you find yourself being chased by dogs or any other creature which tracks it's prey by scent. It is also effective in throwing off human trackers. The caster's footprints disappear at the edge of the stream. Imagine how confusing that would be for Bob, tracker extraordinare, as he contemplates how you managed to hide in a stream that is 1 foot wide by 3 inches deep.

What happens is that the caster, does, literally merge with the water, becoming part of it. This means, of course, that he has no control over where he goes. The caster will be carried downstream at whatever speed the water is moving for the duration of the spell. Of course, the caster can end the spell anytime he chooses and step out of the water. The only way the caster could be tracked is if someone cast detect magic just as he entered the water. The area of water which makes up the caster would glow magical as it is carried downstream.