OutlineBetween Menjangan and PJ, Pemuteran is home to a large artificial reef project known as Bio Rock as well as quite a few outshore reefs. Bio Rock is a series of large metallic underwater structures which have "bio electric" current pumped through them (to promote coral growth). Unlike many artifical reefs around Bali, this one is actually working really well and if you swim to the far end (the oldest part of the artificial reef) you'll probably not even be able to see the underlying metallic structure.
Off shore you have a variety of reefs with Napoleon Reef being the most known one (at least by me). This is basically a sunken atoll in the middle of the ocean which is swarming with life. It's called this due to the Napoleon Rass that were once seen here but I assume they've moved to less human infested waters since I haven't ever seen any here!