Avalon Harbor in Avalon, United States, offers a diverse underwater environment featuring reefs, kelp forests, artificial reefs, and wrecks. Divers access the site from the shore for dives typically lasting 50 minutes. Depths range from 20 to 100 metres, with an average of 45 metres. Visibility varies significantly between 20 and 80 metres. Water temperatures range from 12C to 16C, with thermoclines consistently present at approximately 15 metres, causing a temperature drop of 3 to 6 degrees. Hazards include boat traffic, cold water, deep conditions, entanglement risks, jellyfish, low visibility, overhead environments, rip currents, sea urchins, and surge. Facilities include air fills, showers, toilets, changing rooms, rinse stations, dive shops, guided tours, and gear storage.

The Suejac Wreck is a shore-accessible artificial reef located off Avalon, United States. The structure sits at depths ranging from 18 to 27 metres, with an average depth of 23 metres. Divers experience visibility between 10 and 30 metres and mild currents. Due to the depth and overhead environment, this site requires careful monitoring of bottom time and decompression limits. Divers should be aware of potential entanglement risks and boat traffic near the entry point. A wetsuit of at least 5mm is recommended to manage water temperatures that fluctuate between 14 and 19 degrees Celsius throughout the year.

Casino Point Dive Park in Avalon is a protected marine area featuring a diverse underwater landscape of reefs, kelp forests, and artificial structures. Divers can explore depths ranging from 4 to 32 metres, with a thermocline typically present at 40 feet. The site is accessible via a shore entry and is suitable for beginners, though divers should be aware of mild currents and occasional surge. Visibility generally fluctuates between 10 and 30 metres. Facilities at the park include toilets, showers, rinse stations, and equipment rental services. Night diving is permitted, and the site is well-supported by local dive shops offering air fills and guided tours.

Lover's Cove is a protected marine sanctuary near Avalon on Santa Catalina Island. This shore-entry site features a reef and kelp forest environment with depths ranging from 0 to 10 metres, averaging 5 metres. It is suitable for beginners, though divers should remain aware of boat traffic and potential surf. Marine life frequently encountered includes very common Garibaldi and common wrasses, which are often seen during the summer months. Less common sightings include California sea lions, California spiny lobsters, and scorpionfish. Visibility varies between 3 and 15 metres, and water temperatures fluctuate between 15C and 20C throughout the year.

The Valiant Wreck is a 75-foot luxury yacht that sank in 1930. Resting in Avalon, the site features depths ranging from 27 to 30 metres, with the shallow side at 27 metres and the deeper side at 30 metres. This wreck dive is suited for intermediate divers due to the overhead environment and potential boat traffic. Divers can access the site by boat or shore, though an Avalon Harbor Permit is required prior to diving. Conditions typically include mild currents and visibility between 10 and 20 metres. Water temperatures fluctuate between 14C and 18C throughout the year.

Frog Rock is a reef and kelp forest site located 4000 metres off the coast of Avalon. This site is suitable for beginners and maintains a consistent depth of 13 metres. Divers and snorkellers can expect mild currents and visibility ranging from 5 to 10 metres. Water temperatures fluctuate between 15 and 21 degrees Celsius throughout the year, making a wetsuit advisable. Access to this site requires a boat. The topography features a kelp canopy above a reef structure, providing a manageable environment for those looking to explore the local marine habitat.

Little Farnsworth is a deep pinnacle and reef site located off Avalon. The topography features a significant pinnacle structure surrounded by a kelp forest, with depths ranging from 15 to 40 metres and an average depth of 27 metres. Divers experience visibility between 10 and 20 metres. This site is suited for advanced divers due to strong currents, surge, and the risk of entanglement in the kelp. Access is by boat only, and divers should monitor for boat traffic at the surface. Typical dives last 45 minutes, and it is recommended to time dives around slack water to manage the currents.

Garibaldi Reef, located off Avalon, United States, is a reef site suitable for beginner divers. Reached exclusively by boat, the site sits 2500 metres from shore and offers a manageable experience with mild currents. Visibility typically ranges between 10 and 30 metres. Water temperatures fluctuate throughout the year, ranging from 15C in the winter months to 21C in late summer, necessitating the use of a wetsuit. Divers should remain vigilant regarding active boat traffic in the area and monitor their depth closely during descent and ascent. A surface marker buoy is recommended when surfacing to ensure safety from passing vessels.