Paraiso Bajo

You roll in across from the mouth of La Caleta marina and the water starts moving you north. Two or three low coral ridges lie parallel to the beach, roughly 180 metres off it, with lanes of sand in between. Coral heads three to six metres tall stand out of the sand, hung with sponges and anemones, and grunts, snappers, sergeant majors and queen angelfish sit around them. Nothing here is deep, and most boats work it at nine to twelve metres.

Some guides then turn away from the coral and swim out over open sand towards shore. It looks like a mistake, but the small animals people ask for live in the sand. Scorpionfish sit in it without moving. Peacock flounder lift off in front of you and settle again. Southern stingrays lie in the shallows inshore of the ridges, and somewhere on that ground, if the guide knows the patch, there is a seahorse.

After dark the same ground turns over. Octopus hunt in the open, spotted morays leave their holes, basket stars unfold, and the toadfish calls from inside the coral. Night boats run this reef regularly, and groups from several of them can end up over the same octopus.

Paradise sits on the line where Cozumel's national park begins. The decree that created the park starts its boundary at the north tip of this reef, so the water north of it lies outside the park, and from here south to Punta Celarain fishing is prohibited1.

The reef also has a place in the science of the splendid toadfish. A 2017 acoustic survey here made the first scientific recordings of the species, an endangered fish that dens under ledges on this reef2. The same survey measured what the surrounding traffic adds to the soundscape: a single cruise ship raised ambient levels by up to 4 dB at night and small motorboats by up to 7 dB, in the band the toadfish calls in. Its authors describe the effect on the calls as potential masking and ask for further study2.

The park's management programme lists Paraiso first among the reefs hit by years of high visitor numbers1. Resort courses, certification dives, second tanks and night boats all use it, so the coral shows the wear and the ridges are rarely yours alone.

Most people meet this reef on somebody else's plan: the second tank of a morning boat, a resort course, a night run. Say what you want from it. Asking for time over the sand instead of a lap of the coral changes the dive more than anything else you can request.

Before you go in, the guide checks your buoyancy, and on this stretch that is a condition of diving at all1. Keep fin tips above the ridge tops and do not settle on the coral to hold position for a photograph. Feeding is prohibited in the park, and that includes the morays.

On night dives take a backup light as well as a primary, as operators ask, and wear a non-flashing marker so your buddy can pick you out when several groups meet. The June and July reef rest, a closure of selected reefs that changes each cycle, has included Paradise, so confirm with the shop before building a day around this reef.

The drift runs north, and the Puerta Maya cruise pier lies that way. On a strong day the current can carry you towards the ships, so start the ascent early, with a marker buoy up.