Cetti Bay Overlook Dive – Gun Beach & Tumon Bay
Site Overview
Cetti Bay is a deeper reef site accessed by boat or by a scenic hike along the coastal trail, offering excellent coral diving with clear water and diverse marine life. The reef slopes from approximately 5 to 25 metres with healthy coral formations including table corals, staghorn thickets, and gorgonian fans. Schools of snappers and trevally are common along the reef, while stingrays rest on the sandy patches between coral formations. The site is known for occasional leopard shark sightings during the dry season, adding an exciting big-animal element to the coral-focused diving. The water clarity at Cetti Bay is often exceptional, with visibility frequently exceeding 30 metres in the clear Pacific water. The above-water Cetti Bay Overlook is one of Guam's most popular hiking trails, offering stunning panoramic views of the coastline. The combination of scenic hiking and quality diving makes this a popular day-trip destination for divers who want to combine underwater and above-water exploration. The site is less crowded than the Tumon Bay sites, providing a more secluded diving experience. The coastal trail above provides stunning views of the Pacific Ocean and is home to native bird species, making the entire area a haven for nature enthusiasts who appreciate both terrestrial and marine environments. The reef supports a healthy population of hard corals that provide essential habitat structure for the diverse fish communities.
Dive Briefing
"Descend from the dive boat onto the reef slope at approximately 10 to 15 metres. The reef descends gradually with healthy coral formations covering the limestone substrate. Schools of snappers and trevally patrol the reef edge, while stingrays glide over the sandy patches. Work your way along the reef slope, noting the diverse coral communities and the fish life they support. Leopard sharks are occasionally seen resting on the sandy bottom or cruising the reef edge during the dry season. The excellent visibility allows for appreciation of the reef landscape from a distance. Maintain good buoyancy to protect the coral formations. Ascend gradually along the reef slope, completing a safety stop at 5 metres on the shallow reef top. The dive typically lasts 45 to 50 minutes at these comfortable depths. The reef slope features several large coral bommies that serve as cleaning stations where smaller fish remove parasites from larger species. Take time to observe these fascinating symbiotic interactions before concluding your dive."
Signature Marine Life
Snapper
Lutjanus sp.
Best: January, February, March
Stingray
Dasyatis sp.
Best: January, February, March
Leopard Shark
Stegostoma tigrinum
Best: November, December, January
Grouper
Epinephelus sp.
Best: January, February, March
Trevally
Carangoides sp.
Best: November, December, January
Safety & Hazards
- Access requires hike or boat depending on conditions
- Moderate surge possible on exposed coastline
- Currents can develop along the reef slope
- Boat traffic in the approach area
- Limited exit points if shore diving
Traveler Notes
Who is this for?
Cetti Bay is suitable for Open Water divers and above, with the depth profile accommodating all certification levels when limits are respected. The site is ideal for divers seeking a less crowded reef experience with excellent visibility and diverse marine life. The combination of hiking and diving appeals to adventurous travellers who want to experience Guam's coastal beauty both above and below water. Underwater photographers will appreciate the clear water and colourful coral landscapes. Families with older children who snorkel will find the shallow sections rewarding.
Quick Stats
Dive Logistics
- Coral Reef Ocean World
- Guam Dive Center
- Aqua Sport Guam
- Pacific Divers Guam
Photography Info
Best for: wide_angle