Pulau Bidong is the larges of six islands and several outcrops about 22 kilometers southeast of Redang Island. Bidong was used by the UN as a refugee camp for Vietnamese boat people fleeing the war back home. The island was declared off limits to visitors during that time, with access only allowed in 1999.
Although the area is now accessible, legally at least, few divers visit the island group even though it's not that far from Redang. There is no infrastructure on Bidong, and no regular boat service. Your best chance of diving this area is on a day trip from Redang, although few operators seem to make the trip.