The group, including a diver from Singapore, one from China and four Malaysians, disappeared after going diving off Tioman island on Malaysia's east coast Saturday, an official with the Malaysian Maritime Enforcement Agency.
Only one person with the group, whose members were aged between 25 and 33 and which included two women, resurfaced after the dive, he said.
Three boats and eight navy divers are involved in the search.
Malaysia's east coast islands, famed for their corals and marine life, are a popular dive destination. Accidents are rare.