As my screenname implies, I love long wet hair, but soaking, dripping wet long hair really gets me. I love to see nice freshly brushed hair, maybe tease with it first (the anticipation is hot!) and them get it drenched, either by dunking (tub or even a bucket), or in a pool, or the shower, etc.

The other thing that sets me off is a bunch of shampoo poured over beautiful dry hair, then lathered up.