SHE had dived to World War II shipwrecks off Vanuatu and with whitetip sharks in the Red Sea. By December last year, scuba-enthusiast Carol Martin had clocked up 1000 dives and 15 years as a member of the St George Scuba Club in Sydney's south, but a night dive at Bare Island, off Botany Bay, on February 3 was her last.

Then four weeks after Ms Martin, 52, stopped breathing during the dive, Adam Rothery, another experienced scuba diver, died suddenly at the Royal Sheppard wreck off South Head.

Risky hobby ... dive instructor Tony Patamise, second from right, with students, from left, James Walsh, Adam Arnold and Sean Rhael at Camp Cove. Credit:Jon Reid

His death was the fourth in as many weeks around Australia, leaving the scuba community asking questions about an unusual spate of deaths and cautiously reviewing safety procedures.

On March 5, a 55-year-old father of two, Michael Williams, suddenly lost consciousness during a dive in Melbourne's Port Phillip Bay. One week earlier, Agnes Milowka, a world-renowned cave diver from Melbourne who was a stunt diver in the James Cameron film Sanctum, ran out of air during a dive near Mount Gambier in South Australia.