Modeling underwater produces some of the most visually unique images. Each model greatly differs in their abilities to open eyes, hold breath, achieve neutral buoyancy and pose all the while looking relaxed in an underwater environment.
Holding your breath is one of the main aspects. The longer the model can hold their breath the more shots you can get. One way you can achieve this by staying calm & relaxed.
Hair floating in various directions can beautifully enhance an image. With every movement the model makes, the hair will follow. Moving the head horizontally and tilting the head back and forth is relatively easy. A skilled model can gauge her environment and hold her head in such a way that allows her hair to flow out and away from her face.
This video is to show what goes into modeling while underwater.