Location:  Between Banzai Cliff and Bird Island on the east side of the northernmost point of Saipan Island, C.N.M.I., USA.

Other websites describing The Grotto:  Shorediving.com Underexposed.us saipandiver.smugmug.com

Special warnings:  This is a tough dive for two critical reasons: The entry/exit point is at the bottom of a 111-step staircase, and there are no exits within 1km if you run out of air outside the entry/exit cavern. If you're forced to surface outside The Grotto with very little air, come in Hole 1, the roof of which is barely under the surface (though currents can make this entry impossible for snorkellers and divers near the surface). If you surface outside with no air at all, the best you can hope for is to cling to the boat buoy at low tide outside Holes 2 and 3, or drift down to Bird Island a kilometer away, where you can climb out of the water or attract the attention of sightseers high on the mountain nearby. DO NOT attempt to climb up the cliffside immediately outside The Grotto: it's suicidal. The only time that The Grotto is used for intro dives and open water lessons is the four or five days in Autumn when nearby typhoons make all other dive sites unusable; at these times, these inexperienced divers do their entire dive within the main cavern. There's a port-a-john toilet and a solar-powered emergency phone that's never working, but within an hour's walk there are no residences nor businesses.

Special attractions:  Long ago ranked as the 11th best dive worldwide, back when the lack of a staircase and access road kept tourists infrequent and shy native fish populations high. Spectacular visibility, unique geography including large caverns. Especially for dawn dives and night dives, there's a good chance of seeing big animals such as turtles, reef sharks, rays, tuna, and napoleon wrasses. Except for the aerobic difficulty of the staircase and extreme lack of any nearby facilities, this is the most easily accessed divesite in Saipan, easily reached by normal rent-a-car.

How to dive the site: This dive begins in the parking lot.  Please take precautions against carthieves.  Note the location of the solar-powered emergency telephone, and determine whether it's working. Ideally, leave one person in the car (not merely nearby) and let someone know when you're expected to return to your hotel or diveshop. Don't bother bringing a dive float; consider bringing underwater flashlights. Bring a dive computer or submersible dive planner, since accidentally reaching unexpected depths is easy in this crystal-clear water.

Next, quiz divers exiting the water.  Ask about current outside the cavern, along the underwater cliff.
Conduct your dive briefing using this map and prior to suiting up. Stand at a small fenced-in lookout point at on the map. If other groups are entering or exiting the water below, be sure to watch them do it.

During the briefing, be particularly aware of signs that some of your divers may be searching for an excuse to avoid this dive. It's an intimidating dive, especially for heavy breathers, claustrophobics, those with knee and back problems, and so on.

Gear up in the parking lot. Leave your wetsuit open and loose (to prevent heat exhaustion) and let your fins hang from your BCD's chest strap (to leave your hands free). Wear your BCD and weightbelt normally. Walk down the staircase.

At the bottom of the staircase , look for a stream-like band of water between the cavern wall and the large entry/exit boulder , , . Caution your dive group that this boulder isn't firm: it rocks gently with heavy water surges. Do not swim between the rock and the staircase. There's a word for people who do that: "flat".

Time your next move to happen while the water is low between the rock and the staircase. Stride/hop over to the entry rock. Put someone on the far side to assist & balance your divers while they cross.

Watch other divers exiting at . They hold onto a rope and swim/flop onto the entry/exit rock where it's flat near the water surface.

Walk to the high point on the entry rock, facing the permanent dive float in the center of the cavern. Have your team turn on their air, put on fins, finish zipping up their wetsuits, and do a giant-stride entry here. It's a two-meter drop to the water surface, so look again for signs of unwillingness amongst your divers: people who don't want to make the drop can do a sitting entry at the exit point or wait on this rock until the team finishes diving. Tell your divers to move quickly out of the drop zone. If there's no current, they can simply float at a medium distance. If there's a current and no other team using the rope that connects the dive float to the entry/exit rock, then ask your team to hang onto that rope. If another team needs that rope, then ask your team to descend to 5m/15' and stay together on the rocky bottom. This is a high traffic area, so be sure that your buddies don't accidentally join another team.

In the rough water days before and after a typhoon, just keep your team inside the main cavern. The rock bottom ranges from 15 feet/5m under the dive float to 60~70 feet/18m at Otto's favorite hangout, a flat sand patch at and . Otto is a completely harmless whitetip reef shark, one of three that are almost always napping around The Grotto.

If your team is a lightly experienced crew, take them outside to the underwater cliff via (counting right-to-left) "holes one and two ", perhaps via a large swim-through called "the closet" . The naming convention of "holes 1, 2 and 3" is used by all diveshops on Saipan; "the closet" normally doesn't have a name. The entry to the closet is near 15'/5m deep. Inside the closet there is no surface: the closet's ceiling is at 15'/5m and the floor is at 30'~40'/10~13m. Look for large schools of red hatchet-shaped fish with white "night-light" glow zones under each eye.

Outside holes 1 and 2, there's a broad, shallow shelf at least 60'/20m wide. A boat tie-up float is anchored here, but don't plan to surface here except in emergencies, since the wave action and currents at the surface can be daunting. Also, the float is underwater at high tide and often missing. Look for large schools of pyramid butterfly fish and very small schools of small barracuda. Irresponsible divers feed wieners to these butterfly fish.

Discourage people from going deeper, beyond this shelf. Out there it's deeper than a Harvard professor, and the water's exceptionally clear with no obvious references for scale, so it's very easy to unintentionally go too deep or too shallow. A certain class of diver likes to go deep here, particularly to visit an absurdly deep tunnel called "The Temple of Doom", but this class of diver is known as "dumb and soon to be dead". I'd rather gargle broken glass than send sport divers down there.

If your group is 100% well-and-truly advanced divers, good swimmers, and better than average on air consumption, send them out through the narrow, 65'-deep tunnel called Otto's House or through the enormous, gorgeous churchlike Hole 3 , then out to the left to an underwater cavern called "The Bat Cave" .

The Bat Cave is completely underwater. It's built into the exterior of the sea cliff. Its roof is approximately 45'/15m under water, and the floor about 15'/5m deeper. It's as wide and roomy as a middle-class American's suburban home. Inside one can often see two napping whitetip reef sharks, "sleepy head" and "hook". Hook gets his name from a fishhook permanently imbedded in his lower lip. In the near wall, there's a narrow swim-through . In the far wall there's a low stone shelf. Along the back wall there're one or two deep, dark, tall tunnels that quickly end before your interest is raised, so they're not worth exploring. Around the entrance are bubble corals, some gorgonian sea fans, and some of the red hatchet-shaped fish mentioned earlier.

Come back early. You'll want at least 800 psi / 80 atm in your tank when you reach teh safety stop at the bottom of the entrance cavern's dive float, so plan conservatively. If one-and-only-one of your buddies is unexpectedly low on air, the best-on-air diver can trade tanks with him cautiously underwater when the worst diver reaches almost halfway on air (1800 psi on a 3,000 psi tank)-- but this is not a trick to plan on doing, and it's not for the faint of heart or inexperienced. It's a desperation move.

Come back into The Grotto via Hole Three. Be aware that Hole Three is dark, hard-to-see from the outside, and as violent as Godzilla near the surface, so keep your eyes wide, stay at least 20 feet deep, and expect to do a little hunting around for a tunnel as large as a church and as hard to see as a Black Hole in a night sky. Instead of using up your air outside, leave yourself some air to explore the shallower floor inside The Grotto as you slowly ascend to the bottom of the entry/exit float where you can do your official safety stop.

After the safety stop, have your buddies hold the rope at the surface and go hand-over-hand to the entry/exit rock. At very low tides they may have to shed their fins and climb out; at high tide they can just let a wave push them up onto the rock. Count yourselves as survivors, and rest up for the long walk back to the van.