Calo D'en Monjo, Mallorca: cave and tunnel diving in a U-shaped bay

Calo D'en Monjo is defined by its distinct U-shaped bay topography, situated between two prominent cliffs. Unlike the standard reef slopes found elsewhere in the region, this site is characterized by a complex series of rock formations and geological transitions. The approach typically involves swimming from one side of the cliffs to the other, moving through the water column to enter the primary tunnel system. The seafloor is composed of solid rock, providing a stable but intricate environment for navigation.

The dive profile begins in the shallower zones, where you enter a significant L-shaped tunnel at approximately 5 to 6 metres. This passage stretches for about 25 to 30 metres, offering a change in light and perspective as you move between the cliff faces. As you progress deeper, the topography shifts from simple passages to more complex structures. The descent leads you toward the deeper sections of the bay, where the rocky bottom drops to a maximum depth of around 18 metres.

As you move toward the deeper end of the site, the geology becomes more varied and rewarding for exploration. You will encounter a natural arch and a cavern that contains a small air pocket, providing a classic cave-like experience in a relatively shallow setting. Another tunnel provides further passage through the rock, allowing for a non-linear dive plan. These features require careful buoyancy control to navigate the tighter spaces and to avoid contact with the limestone walls.

The resident fauna is closely tied to these rocky crevices and sheltered openings. You can frequently find moray eels tucked into the rocky cracks and octopus utilizing the various overhangs for cover. Larger groupers often patrol the deeper areas near the 18-metre mark, while sea bream and damselfish move in schools around the shallower sections of the cliffs. The site offers excellent opportunities for macro observation among the smaller organisms living in the cracks.

For those watching the seabed, the rock surfaces are home to a variety of invertebrates. You can find nudibranchs, shrimp, and crabs scattered across the stone, often requiring a closer look to spot. Starfish and various mollusks inhabit the crevices, adding to the biological diversity of the rocky substrate. These smaller creatures are most easily observed when you are hovering steadily near the cave entrances or within the sheltered sections of the tunnels.

The site's primary appeal lies in its structural diversity rather than high-speed pelagic action. The sequence of tunnels, arches, and caverns provides a sense of progression that is rare for such a shallow site. Instead of a simple descent down a wall, you are navigating a three-dimensional landscape of shadows and light. This makes the site particularly interesting for divers who enjoy technical navigation and exploring the architectural details of the seabed.