Investigators into a fatal helicopter crash off an island airport have called for a review of rescue operations in its surrounding waters.

Three men and a woman died when a Super Puma plunged into the sea off Shetland on August 23. There were 14 survivors.

Lifeboats and helicopters were sent to the scene but one rescue boat supposed to leave from a slipway to the west of the airport was delayed due to tidal conditions and took almost an hour to reach the crash scene.