AquaNuts Diving - Lake Malawi, Africa
There are not a lot of dive companies in Malawi, but the diving in the huge fresh water Lake Malawi offers a chance to see hundreds of beautiful cichlid fish. The diving is basic and you don't get to see a lot of diverse marine life, but Aquanuts does a good job of making the dive interesting and the water is pretty much always warm. It was a great place to get certified because of the calm conditions, excellent visibility, and helpful instructors. Night dives are user-friendly and very cool; divers can see predatory fish hunting in their torch lights.
Aquanuts is also home to the Maru Research Center, where visiting divers (or non-divers!) are invited to take part in research of the biodiversity of the cichlid population. Malawi hosts one of the world's greatest populations of freshwater tropical fish, so divers get the sensation of diving inside an aquarium.