This is very beautiful. The model manages to look serene even in what I imagine would be a difficult pose to hold, the reflection of the corals on the surface of the water gives a nice symmetry to the picture and the colours themselves are vaguely reminiscent of classical paintings. Kudos.
To the best of my recollection, she was totally relaxed and wasn't making any attempt to hold a pose. Underwater, I generally just shoot like crazy and catch them moving through the perfect pose. When someone tries to hold a pose I tell them not to, just move slowly and gracefully.
She had been posing for several years in the pool already but we anticipated that it would be more difficult in the ocean. In fact, it was not ...
Off the big island of Hawai'i near Puna there are some very convenient volcanic tide pools that are as much as 20 feet deep but have only a few inches clearance access to the open sea at low tide and so have no large predators ... it's like swimming in a tropical aquarium. It's a perfect place for photography as the ocean fades to a solid blue in 30 yards, giving the illusion of distance.