As you watched Amber and Veronica drifted towards each other and begin feeling up each other's tails while sharing a kiss that could get steam off of the ocean around them. Lauren and Molly both locked eyes on you and you barely had enough time to say "I wish I could breathe underwater!" before both of them hit you like a pair of torpedoes.
They met you in a three way kiss before dragging you under the waves and towards the sea floor. Fortunately it wasn't too far to the bottom because you barely had time to notice the new sensation of breathing water before Lauren literally tore your trunks off of you while Molly relieved herself of the rest of her own suit.
"God damn..." Lauren said between kisses, her voice perfectly audible despite being under water. "I really need to... God damn!" Pinning you against the sandy bottom, she positioned her slit above your erection and lowered herself onto it.
"Mmm..." Molly said as she leaned in close to you and pressed her full breasts into your chest. "Save some for me." She began to nibble at your ear.
Bracing herself on the floor and using her tail for leverage, Lauren started riding you in earnest. You managed to get used to the sensation of underwater sex fast enough that you were soon able to bring her to her first orgasm. Her eyes rolled into the back of her head and she screamed out, her screams taking on a musical quality.
"Oh... I think it feels better as a mermaid. Molly, you better take a turn before I end up hogging him all day."