Twenty-seven young men begin their quest to become members of the Navy's elite Clearance Diver Branch. At the RAN's Diving Training School in Sydney they launch into the week-long Clearance Diver Assessment Test [CDAT]. Overseen by a team of experienced Navy Divers, they will be taken into a physical and mental 'hell' specifically designed to test strength and endurance and weed out the weak.

Now, the real training begins. In the first module of the course the new recruits must prove they can cope with the deep. Clearance divers are often used to conduct deepwater battle repairs to ships and strategic infrastructure. When working under these conditions danger is ever present and small mistakes can rapidly turn into life threatening disasters.

Only thirteen men remain on the course and the training is about to get even more severe. Now, the surviving recruits face the nightmare of Maritime Tactical Operations where sleep will become a distant memory. Clearance Divers must be able to carry out clandestine recognisance operations behind enemy lines. To achieve this they use a special re-breather or bubble free diving set and conduct their operations under the cover of night.

The men of Basic Clearance Divers Course number 67 are deployed to a remote tropical island off the Queensland coast where they must complete the final 'demolitions' phase of their training. It's the part of their course they've been waiting for. They've got thirty tonnes of high explosives, artillery shells and bombs, and three weeks to blow it all up.