To have the possibility operate camera underwater I use Subal housing. This is a waterproof box with flash connectors and controls which allow access to all functions, for convenient and comfortable handling of the camera functions. I work mostly in cold water, in thick dry gloves and comfortable handling is really important for me. I feel it was designed specially for me – so handy it is; I have easy access to any function I need without seeking the button.
One of the greatest problems of underwater photographers is drowning of their cameras. Often it happened in salted or highly mineralized water. In this case it means total death for your camera. This is one of the main reasons why many underwater photographers use cheap cameras. But I know that my Subal housing is more than troubleproof.