Mariana Islands (Guam & Saipan)
United States · Micronesia
Guam and Saipan anchor the Mariana chain with a rare mix of WWII wrecks, dramatic cavern dives, and open-ocean pelagic action where the Philippine Sea meets some of the deepest water on earth.
How this reef is doing
ⓘ How we measure thisReef state
Live science signals for this reef are still being gathered.
Coral cover
Fish life
Heat
Fishing
Open to fishing, and the water is fairly quiet.
Sources · Global Fishing Watch and reef gravity
What you will see
22 species across the dive sites here
African Giant Snail
Seen 25 days ago
at American Tanker Wreck
Galaxy Coral
Seen 27 days ago
at Blue Hole, Guam
Least concern
Lionfish
Seen 27 days ago
at Blue Hole, Guam
Least concern
Green Anole
Seen 29 days ago
at Obyan Beach Reef, Saipan
Least concern
Green Sea Turtle
Seen 1 month ago
at Obyan Beach Reef, Saipan
Least concern
Purple Hermit Crab
Seen 1 month ago
at American Tanker Wreck
Mariana Kingfisher
Seen 1 month ago
at Obyan Beach Reef, Saipan
Blackfin Barracuda
Seen 2 months ago
at Blue Hole, Guam
Least concern
Tracey'S Damselfish
Seen 4 months ago
at Blue Hole, Guam
Least concern
Mourning Dorid
Seen 4 months ago
at Obyan Beach Reef, Saipan
Pacific Bullethead Parrotfish
Seen 5 months ago
at Blue Hole, Guam
Least concern
Indo-Pacific Man-O-War
Seen 5 months ago
at American Tanker Wreck
Napoleon Wrasse
Seen 7 months ago
at Obyan Beach Reef, Saipan
Endangered
Spotted Toby
Seen 8 months ago
at Obyan Beach Reef, Saipan
Least concern
Scorpionfish
Seen 10 months ago
at American Tanker Wreck
Least concern
Cup Coral
Seen May 2025
at The Crevice, Guam
Grey Reef Shark
Seen Oct 2024
at Blue Hole, Guam
Endangered
Scalloped Hammerhead
Seen Oct 2024
at The Crevice, Guam
Critically endangered
Acropora Table Coral
Seen year round
at Obyan Beach Reef, Saipan
Endangered
Batfish
Seen year round
at American Tanker Wreck
Least concern
Giant Grouper
Seen year round
at American Tanker Wreck
Spotted Eagle Ray
Seen year round
at The Crevice, Guam
Endangered
Dive sites
Blue Hole, Guam
blackfin barracuda · grey reef shark · lionfish · tracey's damselfish
The Crevice, Guam
spotted eagle ray · scalloped hammerhead · cup coral · tracey's damselfish
American Tanker Wreck
batfish · giant grouper · scorpionfish · indo-pacific man-o-war
Obyan Beach Reef, Saipan
green sea turtle · napoleon wrasse · acropora table coral · mariana kingfisher