Sipadan is an excellent place to dive, IMO one of the best in Asia. Don't be put off by stories of kidnappings, there is now a full time military guard on the island next to Borneo divers in the old PB [sadly now gone] dive shop. Sipadan has outstanding marine life, in fact it is better now than when Cousteau first saw it, as the dynamite and cyanide fishing methods by the locals that was once common around the island has now been curtailed. Mabul, next door to Sipadan has some of the best macrophotograpy in the region, dozens of different species of nudibranch, Mandarin fish, Leafy Dragons, Seahorses etc etc. The environmental problem mentioned in the previous post, was caused by one of the locally owned dive shops, they pumped their salty waste water from their RO plant back into the aquifyer. Divers on the island are now limited by Malasian government decree. The diving can be spectacular and there is something for everyone shallow or deep. Don't miss it. Layang Layang off the west coast is also very good and shouldn't be missed if you are in the area.