NBM Dive Site Resource
The Grotto (Saipan)
Marpi, Saipan Municipality, Northern Mariana Islands
Saipan’s signature limestone cavern, reached by a long stairway and linked to the open ocean through three submerged openings.
Save this dive site to your free member profile.
Historic Picture Placeholder
Aquatic life at this dive site
What divers may encounter
Three reviewed connections are featured here. Sightings vary by season, conditions, and chance, so they are never guaranteed.
Aquatic life research in progress
NBM is reviewing a likely local species for this position.
Aquatic life research in progress
NBM is reviewing a likely local species for this position.
Aquatic life research in progress
NBM is reviewing a likely local species for this position.
Site media
Photographs
Three views rotate from the published gallery on each visit.
Contributor media
Dive videos
Three featured video positions are reserved on every profile.Published reference location
Location map
The marker shows the public coordinates associated with this profile. Confirm current access, moorings, and departure details before the dive.Map data © OpenStreetMap contributors
Recent field observations
Diver-reported temperatures
Automatically checked observations from dives during the past 14 days. Three reports are visible at a time; scroll for more.A report that passes the automatic checks will appear here with the dive date, diver’s display name, and temperatures at each depth.
Reports are automatically checked for plausible dates, depths, and temperatures. They are observations, not forecasts; confirm conditions before diving.
Why divers know this place
Highlights
Blue cavern light, three ocean openings, swim-throughs, reef fish, turtles and occasional pelagics.
Before you arrive
Access notes
Use a qualified local guide. Expect roughly 116–120 steps, a giant-stride entry and a strenuous exit. The open-ocean passages create an overhead/blue-water environment; no boat relationship is inferred.
Plan within your training
Conditions and hazards
Steep wet stairs, strenuous exit, giant-stride entry, surge, currents, overhead passages, depth outside the cavern and limited direct ascent in covered areas.
At the site
Facilities and support
Roadside visitor area and stairs; dive support, tanks, guides and emergency planning must come from a local operator.
Independent resource notice
This record is a starting point for independent verification. Access, closures, moorings, weather, currents, depth, visibility, operator availability, and site conditions can change without notice. Confirm current information with the responsible operator, property owner, managing authority, or another qualified local source before planning or attempting a dive.