Once he found fame impersonating bespectacled rocker Buddy Holly, and led the Crickets astray on a diving tour of the UK. Now, leading technical diver John Garvin has helped to pull together what could be the most authentic diving movie to date.

James Cameron’s Avatar follow-up 3D movie, Sanctum, is a cave-diving thriller but essentially a rites-of-passage movie, tracking the relationship of young diver Josh McGuire, played by Rhys Wakefield, and father Frank (Richard Roxburgh), in the aftermath of a dramatic cave collapse in the South Pacific

John Garvin, who started O2 Technical Diving in the Turks and Caicos Islands with assistance from Bruce Lacroix, co-wrote Sanctum, was also the film’s diving co-ordinator, his task to lead the cast through a fearsome learning curve.