>>32532796For sex underwater? Well, I assume it would be in a pool for easy surfacing but worse case scenario, hopefully one of the parties carried a spare air or they're doing it in scuba gear.
For the breath holding part, well sometimes snuff is part of the deal but not always. It's partially a breathplay fantasy, where the deprivation is so strong that the sound of desperate gasps for much needed air in a small surface cavity (not specifically that, could be any other air pocket available) is part of the fetish. The whole idea is that they get by without relying on equipment or mermaid transformations or what have you.