A team of American and British cave divers explore the mysteries of Wakulla, a flooded cave in the swampland of Northern Florida. This 240 foot deep pool, fed by one of the world's largest underwater springs, is a favourite Hollywood haunt. Some of the Tarzan films were shot there, as was "Creature from the Black Lagoon", mistitled as it happens as the water is phenomenally clear. But among divers it is famous for the amazing clarity of the water and a vast network of unexplored deep underwater caverns which are irresistible to them.

Using modern equipment the team dive over 5000 ft into this cave at the extraordinary depth of 300 ft. Expedition leader and NASA scientist Dr Bill Stone uses a prototype rebreather - a revolutionary new computer-operated breathing system which allows the team to spend 24 hours under water. A habitat is sunk 100 ft below the surface where the divers can decompress in comfort. The film follows the divers from their spaceship-like "habitat" into caves never looked on by man - and littered with the remains of long-extinct animals.

Space technology and pre-history come dramatically together in this spectacular film. The preparations were prodigious and the resulting film is stunning. Wisely, the authorities restrict access and Leo Dickinson's film records the first dive for nearly 20 years and the deepest exploration of Wakulla Springs on record.