Toilet Bowl Grotto is a unique geological formation at the Coronado Islands, Mexico, characterised by a rocky grotto where surge creates a swirling flushing effect. This advanced site requires boat access and is suitable only for experienced divers due to strong currents and significant surge. Depths range from 6 to 24 metres, with an average of 20 metres. Visibility varies between 9 and 30 metres, and water temperatures typically range from 14 to 17C, though thermoclines can cause temperatures to drop into the low 10s C at depth. Species recorded around this area include California sea lions, northern elephant seals, Garibaldi, and various wrasses and sea stars.

Middle Coronado Island offers a diverse underwater environment featuring a mix of reef, wall, and kelp forest structures. Divers can explore depths ranging from 13 to 19 metres, with an average depth of 16 metres. The site is accessible only by boat and provides visibility up to 30 metres. While currents are generally mild, divers should remain prepared for surge, swell, and shifting currents near the walls. Due to boat traffic in the area, the use of a surface marker buoy is recommended upon ascent. Water temperatures typically range between 15 and 18 degrees Celsius, though thermoclines can occasionally cause temperatures to drop to approximately 10 to 11 degrees Celsius at depth.

Middle Rock is a reef and kelp forest site located off the Coronado Islands. Divers typically explore depths between 12 and 19 metres, with visibility ranging from 10 to 30 metres. The site features moderate currents and occasional thermoclines, requiring careful monitoring of depth gauges. Access is by boat only, and divers should remain alert for boat traffic during surface intervals and ascents. Species recorded around this area include California sea lions, northern elephant seals, harbour seals, Garibaldi, and various wrasses. Due to the current and surge, this site is best suited for those comfortable with changing conditions, and the use of a delayed surface marker buoy is recommended.

Islas Coronado offers diverse underwater topography including reefs, walls, and kelp forests, alongside artificial reef structures. Located over 11 kilometres from the shore, this site requires boat access. Divers experience depths ranging from 10 to 82 metres, with an average depth of 15 metres. Conditions vary, with visibility typically between 9 and 25 metres and mild currents. Water temperatures fluctuate between 11C and 16C, and thermoclines can cause significant drops in temperature at depth. Hazards include cold water, jellyfish, sea urchins, strong currents, and surge. The site provides multiple locations suitable for various skill levels, with typical dives lasting around 45 minutes.

Middle Grounds is a rocky reef situated between the North and South islands of the Coronado Islands. This site features depths ranging from 6 to 24 metres, with an average depth of 15 metres. Divers and snorkellers experience visibility between 9 and 30 metres, though conditions vary. The site is accessible only by boat and is suitable for beginners. Water temperatures typically range from 14 to 17C, with occasional thermoclines dropping to 10C at depth. Hazards include boat traffic, jellyfish, sea urchins, strong currents, and surge. Guided tours, boat charters, and equipment rentals are available locally.

Puerto Cueva is a boat-access reef located off the Coronados Islands. The site features depths between 17 and 22 metres, requiring good buoyancy control. Divers can expect mild currents and visibility ranging from 10 to 30 metres. Water temperatures fluctuate between 14 and 18 degrees Celsius, with occasional thermoclines dropping into the low 10s Celsius at depth. Surge and swell are the primary hazards, necessitating careful positioning relative to the reef. Species recorded around this area include California sea lions, harbour seals, northern elephant seals, Garibaldi, scorpionfish, and various sea stars. This site is suitable for beginner divers, with typical dives lasting approximately 45 minutes.

The Keyhole, also known as McDonald's, is a reef and drift site located at the southern tip of North Coronado Island. The site is defined by a natural archway and a channel, which provides a distinct topography for divers and snorkelers. Depths range from 3 to 24 metres, with an average of 18 metres. Access is by boat only, and the site is suited for intermediate divers due to moderate currents and potential surge. Visibility typically fluctuates between 9 and 24 metres. Water temperatures are cool, ranging from 14 to 17 degrees Celsius, with occasional thermoclines reaching the low 10s at depth.

South Coronado Island offers a diverse underwater environment featuring reefs, walls, and drop-offs. Divers can explore depths ranging from 13 to 24 metres, with an average depth of 15 metres. Visibility typically spans 12 to 25 metres. The site is accessible by boat and is suitable for beginners, though divers should be prepared for moderate currents, significant surge, and cold water temperatures between 14 and 17 degrees Celsius. Thermoclines can occasionally cause temperatures to drop further at depth. Due to these conditions, a 7mm wetsuit or drysuit is recommended. Night diving is permitted at this location, providing an alternative perspective of the site topography.