Styles
Underwater Portraits Without Getting Wet
Underwater portraits are expensive because they are hard: a housing, a pool, a model who can hold a pose while holding a breath. What makes them worth it is light that behaves in a way it never does in air.
What it does to a photograph
Rebuilds the scene beneath the surface with caustics, the moving net of light that refraction throws across skin, and the blue-green falloff that increases with depth. Hair and fabric are given the suspended, slowed movement of water, and the light comes from above as it does in a pool.
Which photo to use
A photo with visible hair helps enormously, since suspended hair is the single strongest cue that the scene is underwater. Front-facing, and ideally not backlit.
What people use it for
Portfolio and creative work, album and event artwork, profile pictures that stand out for being genuinely unusual, and anyone who likes the look and has no intention of getting in a pool.