The Grotto
Saipan's best-known site: a natural tunnel from a high cliff down below sea level that opens to the ocean through three openings between the surface and about 18 m, with a large 'batcave' at 12–15 m and walls, swim-throughs and caves outside. Shore dive reached by 111–112 very steep steps. Operators quote maxima between about 22 m (central cavern) and 30 m. Surge and current can be dangerous and the site is closed by the authorities when the sea is rough.
depth: 0–30 m