Bali is perhaps better known for what happens on top of the water - surfing - than what happens under it. But there are a number of good dive sites around the island and its close neighbors.
Bali's combination of good dive sites, cultural attractions, and other adventure options makes it great destination for those looking for lots of different experiences. You can dive on a World War II shipwreck one day, visit a serene Hindu temple on the shores of a volcanic lake then next, and then go white-water rafting the day after that.
Many people are surprised to hear that Bali has such good diving, since it's better known for surfing, and as most divers know, the geography that makes for good surfing usually makes for bad diving. That's still true in Bali, where the best surfing is along the southwestern coast, while the best diving is along the northeast coast.
The most popular dive area is around Tulamben Bay, on the northeast coast, while other dive centers are the Menjangan Island in the far northwest and around Nusa Penida island off the southeast coast of Bali.
When planning your dive trip to Bali, your first decision is where to base yourself. The most heavily developed area, with the most hotel options, is the southern part of Bali. Unfortunately, this area is quite some distance from the major diving areas. You can expect a drive of two hours or more to the Tulamben area, and it would take you four to five hours to get to Pemuteran. If you just want to make a couple of dives during an extended stay in Bali, then staying in the South and making the commute may be reasonable. However, if you want to do more than just the 'standard' day trip sites, then consider staying in one of the dive destinations on the east or north coasts. For your post-diving decompression time, you may want to 'head for the hills' and spend a few days around Ubud.