Guam, the US territory at the southern end of the Marianas, packs the world's only spot where wrecks from both World Wars lie touching — the Japanese Tokai Maru resting against the German SMS Cormoran II in Apra Harbor — plus the heart-shaped Blue Hole shaft off Orote Point and easy, warm shore dives in protected marine preserves.
Conditions, highlights, and the resident marine life.
Water and air temperature across the year.
Guam concentrates its diving along the sheltered leeward west coast, anchored by Apra Harbor — one of the Pacific's great natural harbors and a layered war grave. The Tokai Maru, a Japanese passenger-freighter torpedoed by the USS Snapper on 27 August 1943, came to rest against the SMS Cormoran II, a German raider scuttled by her own captain on 7 April 1917 when the US entered World War I; both are on the National Register of Historic Places, and a diver at about 33 m can touch a WWI and a WWII wreck at the same moment — the only known site in the world where that is possible. Outside the harbor mouth, the Blue Hole is a natural limestone shaft dropping from a heart-shaped rim at roughly 18 m past a 'window' exit at about 38 m into open ocean along the Orote wall. Easier days are spent on the American Tanker concrete barge by the breakwater, Gab Gab's calm harbor reef, the Piti Bomb Holes marine preserve with its Fish Eye underwater observatory, and Gun Beach at the north end of Tumon Bay. Water stays 28–30 °C year-round; the dry season (roughly January–May, extending into June and December as shoulder months) brings the calmest seas, while July–November is the rainy season with typhoon risk peaking July–September — storms can occur in any month, so wet-season trips need flexible plans.
What makes this dive worth the trip.
25 species you’re likely to encounter on a dive here.
6 signature sites at this destination.
A calm, protected reef inside Apra Harbor off Gab Gab Beach on the Navy base — Guam's classic training and check-out dive. Gab Gab II is a coral mound rising to about 11 m, thick with fish; the adjacent slope runs gently deeper. Shore entry requires military base access (valid ID or a sponsored visitor pass), so most visitors dive it by boat; the Atlantis tourist submarine often passes the mound.
A shallow lagoon in the no-take Piti Bomb Holes Marine Preserve whose 'bomb holes' are actually natural freshwater percolation pits dropping to about 8–9 m. The largest pit houses the Fish Eye Marine Park underwater observatory (built 1996, windows at ~10 m, reached by a 300 m boardwalk), and the protected fish life is dense and approachable — an easy shore dive and snorkel that pairs well with a surface-interval day.
A 90 m-plus WWII concrete supply barge — towed from Honolulu loaded with war materiel, then sunk beside the Glass Breakwater at the harbor mouth after the war. The hull sits in about 14–34 m next to a shallow reef, making it a favorite first wreck: open swim-throughs for novices, deeper structure and penetration lines for wreck-certified divers (do not breathe trapped gas pockets inside). An American flag on the pilothouse is the classic photo stop. Coordinates are approximate (breakwater tip).
A natural limestone shaft in the reef off Orote Point with a heart-shaped rim starting around 15–18 m, dropping past 90 m; divers descend the chimney and 'shoot the hole' through a window at about 38–40 m that opens onto the sheer outer wall, then drift along the drop-off for an open-ocean pickup. Boat access only (about 20 minutes from Cabras Marina) — cliffs make shore entry impossible.
The signature double wreck of Apra Harbor: the 134 m Japanese freighter Tokai Maru (sunk by USS Snapper torpedoes in 1943) lies with an 85-degree port list in about 36–37 m, its upper works reaching ~12 m, resting directly against the WWI German raider SMS Cormoran II (scuttled 1917) at around 33–37 m. Following the hull contours below the Tokai's bridge leads to the Cormoran at about 24–37 m — divers can touch ships from two World Wars on a single dive. Both wrecks are protected historic sites; penetration requires wreck training.
Widely called Guam's best shore dive, at the north end of Tumon Bay inside the Tumon Bay Marine Preserve, named for the rusting WWII Japanese gun on shore. Entry follows pipes/cable through the reef channel onto a slope falling quickly from about 5 m to 35 m-plus, with rich coral growth, resident turtles and octopus, and occasional manta reports. Exposed to swell — dive it on calm days (typically the drier, calmer months) with a buddy who knows the entry.
Local dive centers, resorts, and hotels.
Verified dive centers, resorts, and hotels around Guam will list here — pricing, photos, and direct contact.
