The National Sea Rescue Institute says three naval mariners have died following a rescue operation near Kommetjie in Cape Town.

NSRI Kommetjie duty crew were activated at 14h47 on Wednesday afternoon after an  eyewitness reported what he suspected to be SA Navy personnel washed off a submarine off-shore of Slangkop Lighthouse.

NSRI Kommetjie duty crew responded to the NSRI Kommetjie rescue station to prepare to launch NSRI rescue craft while raising the alarm.

A few minutes later while preparing to launch the NSRI Kommetjie rescue craft, Spirit of the Vines and IL Batello, an MOB (man overboard) alert had been sounded from SA Navy vessels off-shore of Kommetjie and broadcast by Telkom Maritime Radio Services.

At that stage a number of agencies had responded to the scene, and a multi-pronged rescue effort commenced.

Three male casualties were rescued onto one NSRI rescue craft and 4 male casualties were rescued onto one NSRI rescue craft, all 7 – SA Navy Mariners.

CPR efforts were initiated on two of the men and once ashore, at the Kommetjie slipway, CPR was continued on both men by paramedics who, after all CPR efforts were exhausted, sadly they were both declared deceased.

One man was airlifted to hospital by a Netcare 911 air ambulance helicopter in the care of paramedics in a critical condition.

One SA Navy officer remained onboard the naval vessel and in a coordinated operation, during the late afternoon, an SA Air Force helicopter deployed NSRI ASR rescue swimmers and EMS rescue paramedics onboard where an adult female was extricated from the vessel and CPR efforts were commenced.

Despite extensive CPR efforts, the female officer was declared deceased. The body of the female was airlifted to the NSRI Hout Bay rescue station.

The bodies of the 3 deceased have been taken into the care of Government Health Forensic Pathology Services. The 4 remaining crew survivors were lightly injured and did not require hospitalisation.

An investigation will be opened by the SA Navy and maritime authorities.

Western Cape police spokesperson Lieutenant Colonel Malcolm Pojie said an inquest docket was opened. Pojie said that preliminary reports suggest that two men were washed out to sea after the wave hit during what appeared to be an exercise.