Cuevas de Afuera

This is the outermost of the Cancun reefs, sitting past the shelter of the bay on the edge of the Yucatan Current. What that buys you is water: visibility is generally better out here than closer in, and the reef is fed by whatever the current is carrying.

The swim-throughs are the point. Coral has grown across channels in the reef to leave passages you go through rather than over, which is what the name records. Nurse sharks lie up under the ledges, spotted morays sit in the gaps, and stingrays hold on the sand between the coral heads.

Depth stays in a narrow band of fifteen to eighteen metres, which is what makes the long bottom times possible.

The name is worth taking literally but not too literally. Cuevas means caves, and there is a reasonable expectation that a site called the outer caves involves going into something. It does not: these are coral passages with light at both ends, and the honest version of this reef is a pleasant, well-flushed drift at the far end of the line rather than anything cavernous.

What genuinely distinguishes it is position. It is the one site on this coast that sits out on the current rim rather than tucked behind the bay.

It is a long way out, around forty minutes, and it is almost always run as the second tank of the morning after one of the wrecks. That means you arrive with a used tank and a nitrogen load, on the most exposed site of the day. Plan the profile before the boat leaves.

The current is the variable and it is less predictable here than inside the bay. If the guide calls for a negative entry, there is a reason.