Mauritius island, Indic Ocean. More than wonderful.
We've been on honeymoon this year, and in the lagoon, in the private beach of the hotel, 99% of the reef fishes you can see in your LFS were there, one metre deep, 10-20 m from the beach. Every day.
We saw hundreds of species, just in the hotel beach, excepting clown fishes and blue tangs. Trigger fish (even picassos!), tangs, many species of butterflies, frog fishes, lion fishes, pipe fish, dwarf gobies, balloons, hundreds of damsels (which ate bread), many inverts (cucumbers, coral shrimp, etc).
In the beach sports centre (of the hotel) you could borrow free goggles and flips whenever you wanted, and snorkel in the protected area. You could also go daily on a free snorkeling trip on boat, next to the barrier. Plate acropora were more than 3 metre in diameter. There, reef life was ever more astonishing, and corals.
We spent more time under the water than sunbathing ... The water temperature was fantastic, the visibility ... and only 1-2 metre deep. You could see everything without diving.
The hotel was the Long Beach, in Belle Mare. Perfect for a honeymoon or what you like. The island is a must-see. A perfect paradise.