IslaScuba.com: an independent guide to the islands divers travel to, from the Caribbean to the Coral Triangle.
The tropical Indian Ocean is warm all year, and its islands come in two main kinds. Coral atolls, like those of the Maldives, are rings of reef and low sandy islands around a lagoon, with channels that connect the lagoon to the open ocean. Granite and volcanic islands, like the inner Seychelles, Mauritius and Réunion, have boulders, caves and steeper slopes.
The monsoons shape everything. Twice a year the winds change direction, and with them the currents, the visibility and the places where plankton gathers. Divers who understand the monsoon can choose the side of an atoll where mantas feed or where the water is clearest.
Coral in parts of the Indian Ocean was badly hit by bleaching events, especially in 1998 and in more recent marine heatwaves. Recovery varies from reef to reef. The fish and the big animals are still the main reason people come, and many reefs have come back well.
Island by island
About 1,200 coral islands grouped into atolls stretch across the equator south-west of India. The best diving is in the channels, called kandus, where currents bring grey reef sharks, eagle rays and schools of fish. South Ari Atoll is known for whale sharks seen all year, and Hanifaru Bay in Baa Atoll, a UNESCO Biosphere Reserve, draws large groups of feeding mantas in season. Hanifaru is a snorkel-only site.
The inner Seychelles around Mahé, Praslin and La Digue are granite islands with boulder reefs, turtles and reef fish. Whale sharks visit some areas in certain months. Far to the south-west, Aldabra Atoll is a UNESCO World Heritage Site and one of the largest raised coral atolls in the world, reached only on rare expedition trips.
Sri Lanka has two diving seasons on opposite coasts. The west and south coasts are dived from about November to April, the east coast around Trincomalee and Pigeon Island National Park from about May to October. The coast has many shipwrecks, and the waters off the south are known for whale watching.
Mauritius is a volcanic island almost ringed by a barrier reef. Divers explore drop-offs, caves and several wrecks, many of them sunk on purpose as artificial reefs. Nearby Réunion, an overseas department of France, has volcanic slopes and a protected marine reserve along its west coast.
The Andaman Islands in the Bay of Bengal are one of India's few tropical reef destinations. Havelock Island, now officially called Swaraj Dweep, is the main dive base, with dive centers, shallow reefs for training and deeper sites further out.
Off the coast of Tanzania, Zanzibar has easy reefs and Pemba has steep walls and stronger currents. Further south, the islands around Nosy Be in north-west Madagascar offer reefs, turtles and, in some seasons, whale sharks.
In the Maldives, the northeast monsoon from about December to April brings the driest weather, calm seas and usually the best visibility on the eastern side of the atolls. The southwest monsoon from about May to November is wetter and windier, but plankton blooms bring more mantas and whale sharks, especially on the western side. Liveaboards move around the atolls to follow the conditions.
The Seychelles are usually calmest in the change-over months between the trade winds, around April and May and again around October and November. Sri Lanka's two coasts take turns, as described above. Water temperatures in the tropical islands are generally warm all year.
The Maldives are among the best places in the world for a liveaboard, so read our island dive trip planning guide before deciding between a boat and a resort. If you love big animals, compare this region with Pacific island scuba diving, where Palau and the Galápagos offer sharks and mantas too.
Channel dives in the Maldives start on the outside of the reef and use the incoming current to carry divers into the channel, where sharks hang in the flow. Guides usually do a negative entry, dropping quickly to the reef. Carry a surface marker buoy, know how to use a reef hook, and follow the guide's briefing closely. If the current changes, the plan changes with it.
Questions
South Ari Atoll is the best-known area, with whale sharks seen there throughout the year. Sightings are never guaranteed, and local rules on distance and group size apply.
No. Hanifaru Bay in Baa Atoll is a protected area where visitors can only snorkel, with limits on the number of people at a time. Manta numbers there peak in the southwest monsoon season.
Many resort house reefs are calm and shallow, which suits beginners. The famous channel dives often have strong current and are better after you have gained some experience.
Keep exploring