St. Mary's Island - Karnataka Geological Diving

12m Max

5-12m Vis

boat

Site Overview

St. Mary's Island off the Karnataka coast features unique columnar basalt formations created by ancient volcanic activity providing a geological diving experience unlike any other site in India. The hexagonal basalt columns rise from the sandy bottom at 2 to 12 metres creating dramatic underwater landscapes where marine life colonises the rocky surfaces between the geological formations. Parrotfish, damselfish, and various invertebrates inhabit the basalt crevices while sea cucumbers populate the sandy areas between rock columns. The shallow protected waters make this an ideal beginner-friendly site combining geological interest with accessible marine life observation. The island is also a National Geo Heritage Monument adding educational value to the diving and snorkeling experience on this unique west coast destination. The island's designation as a National Geo Heritage Monument adds significant educational value to the diving experience making it a destination for geological enthusiasts as well as recreational divers interested in Earth science. The hexagonal basalt columns visible underwater mirror the spectacular formations visible on the island surface creating a unique continuity of geological features above and below the water line. The geological significance combined with accessible marine life makes this site appealing to educational groups and scientific researchers as well as recreational divers visiting the Karnataka coast.

Dive Briefing

"The dive boat departs from Malpe harbour for the 30-minute crossing to St. Mary's Island. Enter the water near the island's protected side into calm shallow conditions with the basalt columns visible below. Swim along the columnar formations observing the hexagonal rock structures rising from the sandy bottom and the marine life colonising the rocky surfaces. Navigate between the columns observing damselfish defending territories and parrotfish grazing on algae covering the basalt. Sea cucumbers and crabs populate the sandy areas between formations. The shallow depth provides extended bottom times exceeding 50 minutes. Ascend directly to the boat through calm surface conditions. The return journey to Malpe harbour provides time to review geological photography and discuss the columnar basalt formations observed both above and below the water surface. The return journey provides time to review geological photography and discuss the volcanic processes that created the columnar basalt formations observed during the dive."