DeeperBlue.net: General, dive travel and technical diving forums.
Scuba Addict: Forums and photo galleries.
Scuba Board: Articles and message boards about scuba diving, underwater photography and equipment.
Scuba Forum: Monitored discussions of news, articles and editorials about dive travel, liveaboards, scuba equipment, dive safety, marine conservation and consumer issues.
The Scuba Stop: Discussion forums covering equipment, diving specialities, training, dive locations and travel.