SUB THAT SPRUNG A LEAK GOING HALF A MILE DOWN

MINI-SUBMARINES played such a crucial role that the teams clocked up more than 1,000 hours in these underwater camera pods.

Producer Orla Doherty took part in about half the missions, spending more than 500 hours in submersibles, capturing on film such odd creatures as sea toads, which march across the ocean bed on their stubby pectoral and pelvic fins.

Many dives went down about half a mile with the descent alone taking about an hour — but the crew would still have to spend eight hours filming. ‘That’s a long time to go without a loo break,’ says Orla.

There was a heart-stopping moment for her when, a third of a mile below the icy surface of the Antarctic Ocean, the intense cold damaged the seal on one of the pressure gauges. It began to leak, and a pool of water gathered at the bottom of the sub.

For 20 minutes the crew worked frantically to find the leak and fix it before it ripped or ruptured, which would have meant instant death.