Skull Reef is a volcanic reef and artificial reef site located in the Marietas Islands, Mexico. The site features depths ranging from 2 to 23 metres, with an average depth of 12 metres. Access is by boat only, as the site is situated 35 kilometres from the shore. Conditions vary, with visibility typically between 5 and 18 metres and mild currents. The site is suitable for beginners and offers a high rating for snorkelling. Hazards include potential entanglement, jellyfish, rip currents, sharp coral, stonefish, and surf. Water temperatures fluctuate throughout the year, ranging from 21 to 30 degrees Celsius.

Las Tres Marietas features a diverse underwater landscape comprising reef, wall, and cave formations. Located 35 kilometres from shore, this site is accessible only by boat. Divers can explore depths ranging from 6 to 23 metres, with an average depth of 12 metres. Visibility typically spans 10 to 30 metres, allowing for clear navigation of the varied topography. While currents are generally mild, the site presents hazards including surge, swell, and overhead environments within the caves. Beginners should exercise caution near cave entrances and remain aware of their positioning relative to the walls. Water temperatures fluctuate between 21 and 30 degrees Celsius throughout the year.

Anegados is a reef and cave site located in the Marietas Islands, Mexico. The topography ranges from 9 to 25 metres in depth, with an average of 17 metres. Divers must access the site by boat due to hazardous surf conditions at the shore. The site features cave formations that require technical awareness, and conditions include moderate to strong currents. Visibility varies significantly from 7 to 30 metres. Water temperatures fluctuate between 21 and 30 degrees Celsius throughout the year. Due to the depth, current, and overhead environments, this site is suitable for advanced divers only. Guided tours are strongly recommended to navigate local current patterns effectively.

El Morro is a series of stone mounds located in the Marietas Islands, offering a challenging environment for advanced divers. The site features a complex topography of rocky walls, caves, and tunnels, with depths ranging from 18 to 40 metres. Due to strong currents and the presence of overhead environments, this site is suited for experienced divers. Visibility typically ranges from 15 to 36 metres. Access is by boat only, with dives averaging 50 minutes. Species recorded around this area include spotted eagle rays, king angelfish, panamic green morays, Cortez angelfish, razor surgeonfish, wrasses, groupers, guineafowl puffers, triggerfish, rock cod, pufferfish, flower urchins, barberfish, and porcupinefish.

Spearmex is a boat-access reef located 5000 metres from the shore of El Morro, Mexico. The site features depths ranging from 9 to 21 metres, with an average depth of 15 metres, making it suitable for beginner divers. Conditions are generally manageable with mild currents and visibility between 9 and 24 metres. Water temperatures fluctuate between 23 and 30 degrees Celsius throughout the year. Divers can access air fills and a dive shop nearby, though it is recommended to confirm equipment rental availability with the operator before departure. Morning boat trips are often preferred to ensure calmer surface conditions for the transit to the reef.

Morro Grande is a marine dive site located in the Marietas Islands, Mexico. The site features a consistent depth of 16 metres. Water temperatures at this location fluctuate throughout the year, ranging from 22C in April to 30C during the warmer months of July, September, and October. Given the consistent depth profile, this site is suitable for divers comfortable with a fixed-depth environment. Access to the Marietas Islands is typically by boat. As a marine environment, the site supports a variety of regional reef fish and invertebrates, though specific species observations are not recorded for this location.

Caletas is a marine site located near Chimo, Mexico, featuring a combination of natural reef and artificial reef structures. Accessible only by boat, the site offers depths ranging from 7 to 30 metres, with an average depth of 16 metres. Conditions are generally mild, with visibility typically between 10 and 18 metres. The site is suitable for beginners and supports night diving. Divers should be aware of potential hazards including jellyfish and sharp coral. Guided tours and equipment rental are available through local dive shops. Typical dives at this location last approximately 45 minutes.

Chimo is a marine dive site featuring reefs, pinnacles, and a drop-off. The topography includes rock formations known as Las Iglesias, which rise from the seabed like pillars. Divers can explore depths ranging from 9 to 30 metres, with an average depth of 25 metres. Due to the strong currents and depth, this site is suitable for intermediate divers. Access is by boat only, as the site is located over 40 kilometres from the shore. Visibility varies significantly, ranging from 4 to 30 metres depending on conditions. Water temperatures fluctuate between 21C and 30C throughout the year.