I spent much of the first half of '98 working in Guadeloupe, and managed to get in a few dives while I was there.
The main land area of Guadeloupe is formed from two islands joined by a short road bridge. Grande-Terre is the developed island, formed of limestone, with all of the Hotels and amenities (very south of France). Basse-Terre is a (relatively) dormant volcano covered in rain forest. Most of Basse-Terre is a national park, famed for its wildlife and waterfalls, and on one side this extends out to sea around two small islands forming the 'Reserve Cousteau' marine park.
These islands are known, jointly it seems, as Pigeon Island and are surrounded by a coral reef that Jaques Cousteau rated as one of the best 10 dive sites in the world. Here you can dive a typical Caribbean reef where the fish are protected from spear, line and net fishing.
An interesting feature is the 'hot spring', an area about a six feet across, devoid of coral, where the sand is warm on the surface and warmer as you dig down, a result of hot water welling up from the nearby volcano.
All divers below CMAS ** (PADI Rescue Diver) are escorted so deliberate damage to the coral is unheard of, although there were signs of the odd accident.
Viz. is great at 15m on a bad day (usually 20m+), and most people are more than warm enough in shorties (coolest water temperature I saw was 78°f/27°C at 22m).
It takes under an hour to drive from the hotels in Gosier (Grande-Terre), across the bridge, along the windy, hilly, road through the rain forest to the dive schools in Malendure. Really, though you should plan for much longer and visit some of the waterfalls!
Boat trips to the island are brief and you are quickly into the water for a one tank dive.
I did all my dives with 'Les Heures Saines' (+590 98 86 63) who have a wonderfully Caribbean end to the dive - a chilled Planters Punch served as soon as you have your gear stowed. This and all equipment hire is included in the price which is about the same as a two site, air 'n' lead trip, in the Keys.
A rather fun way to spend a Sunday afternoon I must say.