It's a relatively short walk for you and your girlfriend down the street and to the beach. You ignored the stares, the gawks, the stunned double-takes, and just focused on the end result - the beach.
The moonlight glistens on the ocean water, and for a short while, you and she stare at it, transfixed.
"You ready?" You ask her, looking down to her shining yellow eyes. She looks back up at you, slowly blinking those eyes and fluttering her gills.
"Yeah. I... can... can you feel it? In your chest? Like... lungs... pushing out the air..."
You think for a moment. You're not breathing in, and when you try, you find that you can't. But you are pushing the air out very quickly. "We're losing our lungs," you say, coming to the realization. "This is it. Go to the ocean forever or die. Let's go."
"Race you," she says, and pushes forward, running for the very last time towards the water.
You're taken aback, but it takes you very little time to race after her, matching her pace and overtaking her. Your legs are longer, after all.
After you hit about waist-deep into the ocean, you can feel the panic sinking in. You can't breathe. You're no longer pushing air out. You can feel your lungs shrivel up into nothing, and steadily be replaced by a different organ inflating within you, like a balloon. You remember vaguely from biology in high school something called a "swim bladder" that some fish have, basically a sac of air inside that allows the fish to control its bouyancy. You can only assume that this is what you have developed in place of your lungs, but think of it no longer as you dive under the surface.
Your vision is clear, perfect, better than you'd have ever imagined. Even at night, the ocean is illuminated to you. As you zip through the water faster than any human has ever swam, you see the sand deepen, and then sharply drop off. Coral reef, oceanic wildlife of all types, massive kelp forests, and much more that you can hardly identify rocket past you as you continue on to your destination.
[Honey? You there?] you call out with your newfound telepathy.
[Way ahead of you, slowpoke. Stop sightseeing and catch up already. You feel the pull, don't you? Like we're late for an appointment. We have to keep moving.]
You ponder this as you accelerate your swimming pace, steadily seeing her in the distance. You don't know how she got so far ahead, must have been while you were watching the reef. But now that she mentions it, you CAN feel the pull. You've got someone to meet down here, and that someone is waiting, anxiously.