Wet-for-dry is a term in the film industry for a special effect wherein an actor or prop is filmed in a water-filled tank, then imposed onto the film most often via Chroma Key or similar technology. The purpose of this is either to facilitate Slow Motion or to create the image of a supernatural creature not entirely bound by gravity. Filming in water works most effectively on hair and other long, flexible appendages, so expect this effect to take full advantage of such.