Mauritius
Reunion Island (Île de la Réunion) is a small French island in the south Indian Ocean, very close to Mauritius and not so far from Madagascar.
It is mostly reknown for the beauty of its landscapes and ease for hiking. There is such a great number of well maintained hiking routes, going through very different landscapes. As a comparison, it is pretty similar to Hawaii, but all in one island !
The island (roughly 50x70 km) can be divided in two parts, with the old volcano (3000 m) in the west covered with a lush green primary forest, and the active shield volcano (2500 m) in the east with lunar landscapes.
Diving activities are mostly present on the west coast (and a little in the south). Conditions are overall good and easy for diving (not much current, temperature between 24 and 27°C, only high swell sometimes makes life a little harder). Life here is not as abudant as in Mayotte and other hotter waters of the Indian Ocean. You will encounter mainly coastal species not too far from the shore as depth increases very quickly. Most of the time I am looking for small critter : sea slugs, leaf scorpion fish, many beautiful crustaceans there, ghost pipefish if lucky... many different species of morays as well.
Occasionally you will encounter humpback whales during migration (August until end of October). Whale sharks and hammer heads have been spotted on very few occasions as well. In recent years, there have been a number of Bull shark attacks but these animals have almost never been observed during diving...
If you are looking specifically for a diving destination, clearly this is not the place. But if you are looking for a great trip overall on a paradisiac island with some easy diving, I would recommend without any second thought. Plus food is great !