Two bare butts have stopped moving—they bob in the surf, fixed in place. The owners’ faces stay submerged beneath masks and snorkels. They’re clearly watching something.

Earlier today when we arrived at Amedee Island, an hour’s ferry from Nouméa, New Caledonia, the boat crew told us the reef fish were friendly. These guys bring bread to prove it. But the beach was the idyllic postcard kind, with fine white sand and an endless view of turquoise water. We’re nudists on holiday: We wanted to frolic.

And so after a few hours of sun tanning our behinds, exploring the walking paths, and noshing on a spread of deer sausage, poisson cru, taro pudding and heaps and heaps of other local flavors, I’m ready for a swim.

When that couple still stays put, transfixed, I kick out in their direction.

Less than a minute passes before a knob of a head peers up at me. A green sea turtle. A remora, long and thin like a torpedo, wiggles above its shell, attempting to attach.

I kick closer. The turtle puts another foot of distance between us, then pauses, dropping down among a sea grass bed. It’s watching me back. Then it pushes up to sneak a breath. I float in closer. And so the next 20 minutes pass. The turtle takes a stroke for every few of mine, but it’s hardly rushing. Its eye tracks me as we swim over corals, passing schools of unicornfish, 30 strong, and butterflyfish in pairs. This turtle is surely accustomed to visitors and likely hopes for a handout, which I haven’t packed (no pockets on a birthday suit). But even as it must figure I have no food, it stays.

When I find us over finger corals stretching just a few feet from the surface, I pause—the space is too narrow for one of us. It’s time to turn back, and yet, my legs stay still. This started as just another skinny dip in paradise and now I can’t lift my eyes from the turtle. As it slowly strokes to deeper water, I linger, not ready to let go of the moment.