3 caverns · down to 91 m (299 ft) · 3 suitable for an intro team
Cave diving in the Mariana Islands
- Caverns3
- Max depth91 m (299 ft)
- Water temperature27–29 °C (81–84 °F)
- Dive centres4
Diving and fills
Dive here with
Why come here
The Mariana Islands are raised limestone islands in the middle of the Pacific, with three famous overhead dives a short flight apart. On Saipan you carry your gear 112 steps down to the Grotto, a collapsed cave where the light through three underwater openings makes the water glow blue. Off Rota sunlight falls in columns through the roof of Rota Hole, and off Guam you sink down the shaft of the Blue Hole to a window into the blue.
Daylight is always in reach and you dive with local operators; these are not cave dives in the usual sense. The water is warm and clear, but the open ocean is right outside: currents and surf decide which site it is on the day, and Rota has no recompression chamber and no nitrox.
Don't miss
- The Grotto (Saipan): a collapsed limestone cave with three openings to the sea, whitetip reef sharks and usually more than 30 m of visibility.
- Senhanom Cave (Rota Hole): columns of sunlight through the roof, with schools of redfish and sweepers; the light comes in from mid-February to late October.
- Blue Hole (Guam): a shaft in the reef with a window at ~40 m to the open sea, where large fish and sharks often pass along the wall.
On a rest day
- Mount Tapochau: Saipan's highest point (474 m), up a long, rough road and concrete stairs, with a view over the whole island and information boards about the fighting in the war.
- Mañagaha: An islet in the lagoon off Saipan's west coast, a short boat trip away, with wide sandy beaches, snorkelling and remains of Japanese fortifications from World War II.
- Banzai Cliff: Historic site at the northern tip of Saipan, where at the end of the Battle of Saipan (1944) hundreds of Japanese civilians and soldiers jumped from the cliff; part of a National Historic Landmark District.
- Swimming Hole (Rota): A small, naturally formed pool of seawater on Rota's coast.
All 3 caverns
| Site | Max depth | Type | Certification |
|---|---|---|---|
| Blue Hole (Guam)Backmount · Open water / no overhead | 91 m (299 ft) | Backmount | Open water / no overhead |
| Senhanom Cave (Rota Hole)Backmount · Open water / no overhead | 24 m (79 ft) | Backmount | Open water / no overhead |
| The Grotto (Saipan)Backmount · Open water / no overhead | 40 m (131 ft) | Backmount | Open water / no overhead |
Certification requirements, configurations and trimix depths are estimates for planning. Always check them locally and dive within your training.
Map
Dive centres and fill stations
4 dive centres, fill stations and instructors
Blue Palms Dive Service (Rota)
Rota
Guided dives: Senhanom Cave (Rota Hole)
Dive centre on Rota with boat dives, intro dives, courses, snorkelling and fishing trips; website in Japanese and English. Its dive site map gives a light calendar for Rota Hole. Nitrox is not available, according to Dive Rota.
Let's go Diving (Saipan)
Saipan
Guided dives: The Grotto (Saipan)
Dive operator on Saipan for fun dives, snorkel trips in the Grotto and island tours, with a website in English and Japanese. Describes the Grotto as a shore dive and also dives Spotlight, a cavern reached by boat that by its own account can only be dived from July to mid-September.
Micronesian Divers Association (Piti, Guam)
856 North Marine Corps Drive, Piti, Guam
Guided dives: Blue Hole (Guam)
Dive centre in Piti with daily boat dives from Cabras Marina in Apra Harbor (two tanks, 8:30 am show time) and rental. Teaches PADI Tec 40, 45 and 50 (backmount or sidemount) and rebreather courses (Prism 2). Nitrox or trimix fills are not on its website: ask.
Sea People's Rota
Songsong Village, Rota
Mainly freediving, but also daily scuba boat dives (at 9:00 or 13:30), with equipment rental included. Its own site names no dive sites.
Order: partners first, clearly marked as partner; then dive centres by distance from Garapan (Saipan) and independent instructors by name. Not a recommendation: check what they offer yourself.
On this list, or should you be? Get a free partner card →Practical info: rules, fills and emergency numbers
Emergencies
- 911. Rota has no recompression chamber; the nearest is the US Navy's on Guam, half an hour's flight away (Dive Rota). According to the Navy (2015) it is the only chamber in Micronesia that also treats civilians. A working chamber on Saipan is not confirmed. Take diving insurance such as DAN.
Access and rules
- Access: the dive operators pick the sites on the day, by weather, sea and your certification and experience; no particular site is ever guaranteed (Dive Rota). Outside the Grotto you need a guide.
Gas and fills
- Gas: no nitrox and no technical diving on Rota (Dive Rota); on Saipan and Guam not confirmed: ask. MDA on Guam teaches tec and rebreather courses.
Water and season
- Water: 27–29 °C year-round on Saipan according to Let's go Diving, usually 80–84 °F (~28 °C) off Rota according to Dive Rota; a 3 mm suit is enough. Visibility usually 30 m or more.
- Season: typhoons can close flights and harbours (Blue Palms, July 2026).
Getting around
- Travel: Guam (GUM) and Saipan (SPN) have international flights; Rota is reached by a local flight from Guam or Saipan (Star Marianas Air or Micronesia Air Connection Services). Between the islands you fly: follow DAN's rules for flying after diving, also on the low-flying planes (Dive Rota).
Good to know
- Read this first: the Mariana Islands have no cave diving in the usual sense, but three famous overhead dives with daylight in reach: the collapsed cave of the Grotto on Saipan (shore dive), Rota Hole off Rota (boat dive) and the shaft of the Blue Hole off Guam (boat dive). Saipan and Rota belong to the Northern Mariana Islands; Guam is a separate US territory.
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