Gun Beach is located at the northern end of Tumon Bay, Guam, offering a diverse underwater environment that transitions from shallow, protected coral areas to deeper reef sections. Divers and snorkellers can access the site from the shore, with the reef located approximately 50 metres out. Depths range from 1 to 40 metres, with an average of 10 metres. Conditions include moderate currents and visibility between 18 and 23 metres. Water temperatures remain between 28 and 30 degrees Celsius, though some find the water cooler than other island locations. Facilities at the beach include parking, toilets, and showers. Hazards include sea urchins, sharp coral, surf, and strong currents.

Tumon Bay is a 1.5-mile long sandy beach in Guam featuring a large lagoon and a reef drop-off. The site is suitable for beginners in the shallow lagoon, while the drop-off provides more depth for experienced snorkelers and divers. Depths range from 1 to 30 metres, with an average of 1 metre in the shallows. Visibility varies between 5 and 30 metres. Access is via the shore, and the site offers facilities including equipment rental, parking, toilets, and showers. Be aware of potential hazards such as boat traffic, jellyfish, rip currents, sea urchins, sharp coral, and strong currents. Night diving is available at this location.

The Tunnel in Tumon Bay is a shore-entry dive featuring a natural reef tunnel that begins at 10 metres and exits at 14 metres. The topography includes extensive coral formations, caverns, and sand channels. Divers can expect moderate currents and visibility ranging from 20 to 40 metres. With an average depth of 12 metres and a maximum of 18 metres, this site is suitable for beginners. Hazards include sharp coral, lionfish, and the overhead environment within the tunnel. Water temperatures remain consistent throughout the year, typically between 28 and 30 degrees Celsius.

Octopus Reef in Tumon Bay, Guam, is a diverse site featuring surge channels, vertical walls, tunnels, and steep amphitheatre-like slopes. Located 177 metres from shore, this site requires boat access and is suited for intermediate divers. Depths range from 5 to 12 metres, with an average of 16 metres. Divers experience moderate currents and visibility between 30 and 45 metres. Water temperatures remain warm throughout the year, ranging from 28C to 30C. Hazards include surge, sharp coral, and overhead environments. Species recorded around this area include wrasses, striped surgeonfish, Pacific sailfin tang, and various moray eels.

Marine Lab is a reef dive site located in Tumon Bay, Guam, accessible via a shore entry. The site features an average depth of 19 metres. Divers should be prepared for variable conditions, as the area is subject to strong currents and surf. Due to these environmental factors, the site is suited for intermediate divers. Facilities available at the location include parking and toilets. Night diving is permitted at this site, with typical dives lasting approximately 45 minutes. Visibility at the site generally ranges between 6 and 12 metres. Hazards to be aware of include sharp coral, strong currents, and surf.

Fish Eye in Apra Harbor features a combination of natural reef and artificial structures accessible via a shore entry. The site is suitable for beginners, with depths ranging from 1 to 12 metres and an average depth of 8 metres. Divers and snorkellers experience mild currents and visibility between 6 and 10 metres. Water temperatures remain consistent between 28 and 30 degrees Celsius throughout the year. Facilities at the location include parking, toilets, and a cafe. Due to active boat traffic in the harbour, divers should maintain high situational awareness and deploy a surface marker buoy during ascents.

Piti Bomb Hole in Apra Harbor is a shallow reef site accessible via a shore entry. Located 69 metres from the shore, the site features an average depth of 8 metres, with a range between 5 and 11 metres. Conditions are generally mild with visibility ranging from 10 to 30 metres. The site is suitable for beginners and those seeking a refresher dive. Divers can observe a variety of marine life, including common wrasses and Pacific doublesaddle butterflyfish. Less frequently encountered species include emperor angelfish, Napoleon wrasse, titan triggerfish, snowflake moray, longhorn cowfish, Indian lionfish, day octopus, regal angelfish, Brummer's moray, rock cod, masked bannerfish, and blackback anemonefish.

Piti Canal in Apra Harbor, Guam, offers a shallow dive experience across reef, seagrass, and artificial reef habitats. With an average depth of 6 metres, this shore-entry site is suitable for beginners, though divers should be prepared for strong currents and surf. Visibility varies significantly, ranging from 9 to 45 metres. Marine life recorded here includes wrasses, pufferfish, and yellow tang, alongside less common sightings such as Spanish Dancer, spotfin lionfish, day octopus, and giant moray. The site is also accessible for night diving, with typical dives lasting around 60 minutes.