Indonesia, the finest dive resorts available. Submerged, immaculate marine coliseums await the diver, the myriad fish and invertebrates that shelters among and encrust the rugged surface provided by the clumps, shelves and branches of coral are overwhelming in their numbers, shapes and colors, all are reminder of a time when all the life on earth existed in shallow, tropical seas will make you feel stepping into time machine.
Indonesia consists more than 17,000 islands and becomes the largest archipelago in the world with at least 80,000 kilometers of coastline. The special conditions of this strategic zone are the reasons for the fish population to be extremely abundant here.
About 4000 different species are found in the Indonesian waters (over 25% of the planet's fish species), in comparison to the 1000 found in the Red or the 400 from the Caribbean
Apart from this, invertebrates proliferate throughout the hundreds of patch reefs, sheer walls and barriers reefs Colorful branch, pipe fishes and seahorses roam amongst the chrynoids, gorgonias and soft corals, a whole rainbow hue covering the entire extension of the reef walls. Big fish pop up every now and then, offering superb sights of big tunas, shoal or barracudas, manta rays and sharks galore.
Another "rarity" also to be found there is the dugong, an impressive marine herbivorous relative of the manatees, unique survivor of the syrenid order It is also possible to spot several species of cetaceans, from tiny porpoises to the huge Sperm whale.
Indonesia's dive sites are considered to be among the best in the world. Key dive and holiday destinations include: Bali, Lombok, Java,Nusa Tenqqara, Sulawesi,Sumatra and West Papua.
Diving all year around possible, best time is May to September
Water 26° to 30°C (most places though some places like Nusa Penida, Komodo islands or Lembeh Strait can be much colder)
Visibility is mostly very good (up to 30m)
I attached the map for you, have a nice trip.