I worked for 3 months as a scientific diver in the Port Launay area of Mahe, and I found the range and diversity of dive sites very impressive. The coral reefs around Mahe are by no means the most colourful or diverse in the world, and have been damaged by the tsunami, bleaching events, and construction work on the island. However, they are recovering, and there are still many coral varieties to be seen, along with thousands of species of tropical fish and invertebrates. Common fish include bumphead parrots, humphead wrasse, white tip reef sharks, eagle rays, frogfish, stonefish, puffer fish, whale sharks, and loads of angels and butterflies.
My top-five commercial sites around Mahe are:
L'ilot (18-20m): Dives here circumnavigate the tiny granitic islet on the north edge of Beau Vallon Bay. There is a beautiful garden of soft corals and giant clams, and loads of fish, including parrotfish, tunas, potato groupers, butterfly fish, angels, surgeons, eagle rays, and huge shoals of snappers that envelop you. There are often hawksbill turtles to be seen, and octopus, lobster, and eels. The mystical whale sharks also like to hang around here when they're in town.
Aquarium (12m): A great site, and the name doesn't lie. Two large coral bombies in Beau Vallon Bay, which are covered in millions of fish, especially little damsels, angels, anemone fish, butterflies, surgeons, and puffers. I have also seen green turtles here. It is very colouful, and perfect for inexperienced divers.
Shark Bank (35m, good from 18m): Massive granite boulders are surrounded by huge schools of fish, including snappers and barracudas and large numbers of bumpheads, eagle rays, and marbled sting rays. It is a great easy deep dive, with a real feel of the big blue about it.
Ennerdale Wreck (30m): In between Mahe and Praslin, this large wreck is not complete, but still very interesting to explore. There are fewer fish here than at other sites, but if you enjoy challenging dives, you will like battling your way around in the killer current often present here.
Baie Ternay (depending on tide down to 16m): This is a beautiful sheltered bay that is part of a marine park, so it has one of the best abundance and diversity levels of fish and coral. I regularly saw hawksbill turtles here, and it is possible to snorkle from the shore, where there are fish juveniles and sub-adults hiding in the sea grass, far onto the reef.
There are several operators in Beau Vallon. I can recommend the Underwater Centre at the Coral Strand Hotel (www.diveseychelles.com.sc) and Big Blue Divers farther up the beach at Vacoa Village (www.bigbluedivers.sc). Dives cost from about SR150 ($25) for short range, including equipment.
Underwater fanatics should plan their holiday to coincide with the week-long Seychelles Underwater festival (SUBIOS) held annually May, centred around Beau Vallon. There are many interesting lectures, movies, and displays given by visiting eminent scientists and filmmakers and water-sport events for adults and children.