How to Dive for Pirate Treasure

Three centuries ago, Île Sainte-Marie, an island off the coast of Madagascar, was a haven for pirates such as William Kidd. In 2015, Aldo Kane dived among the sunken wrecks in its waters, in search of Kidd’s ship, Adventure Galley. “It’s like a Boy’s Own adventure,” says the Scot. “You’re diving for Captain Kidd’s treasure and you find this bar of silver the size of a book, with a skull and crossbones on it.” Once the wreck was located by sonar, Kane began his dangerous work, diving three to four times a day with a camera crew in attendance. Here are his five rules when embarking on an excavation…

Enlist a first mate

“The buddy system is vital underwater. They check my kit, I check theirs. You’re going down there with air hoses and extractor pumps – stuff that can get snagged, go wrong, or get snared on your life-support system. You have one person working and another keeping watch over everything.”

Don’t get silver doubloon fever

“It’s frustrating when you get a glimpse of 800-year-old Chinese porcelain between the ballast stones [rocks used as weights to stabilise ships] and you have to return to the surface. But if you start to take risks, accidents happen. We shouldn’t be underwater in the first place, so we’re governed by decompression limits and times. When things go wrong, it happens very quickly, especially during an excavation.”

The 55kg ‘silver’ ingot. A UNESCO examination later determined that it is, in fact, 95 per cent lead

Leave a breadcrumb trail for yourself

“When excavating silt, you reduce visibility down to near zero – it’s like diving in pea soup. The danger is that you get disorientated. We have comms so those at the top are able to talk to us; there are surface marker buoys so people can see where each diver is at all times, and we run reels out to each specific dive site, so if you do ever lose direction, you can swim along to one of these.”

Don’t get snagged when you’re down there

“The main risk with any wreck is entrapment. You’re looking for treasure in the cavities under the silt, going into holds where these bars of silver are kept, and you’re wearing all this kit, sometimes with two cylinders. It’s easy to get snagged.”

Maintain control of your breathing

“As soon as you encounter a problem underwater, you’re on the timer – the sooner you can get someone to a hyperbaric chamber, the better. So you try to train your brain to remain calm, concentrating on slow breathing. It tends to slow everything down and gives you that headspace to be able to make decisions. When something goes wrong, it’s very easy to hoover up all of your air.”