How To Rescue The World's Biggest Cargo Ships

Enormous container ships ferry goods all over the world, but when one of them gets into trouble – as happened with the Ever Given and Ever Forward recently – how can they be saved? Chris Baraniuk finds out.

Rain lashed the windows. A violent sea pounded the steel hull of the ship and outside the port of Hong Kong. Her crew had evacuated but standing on the bridge in his life jacket, prepared for the worst, was salvage master Captain Nick Sloane. He beheld the force of the typhoon that now, in the darkness, raged over the stricken vessel. Sloane was holed up with just five other members of the salvage team. Days earlier, they had arrived to the South China Sea with the aim of saving the Kota Kado. When typhoons were forecast to batter the grounded ship, Sloane made the decision to stay on board overnight with a skeleton crew. He wanted to feel how the vessel flexed in the storm, to understand where it hit her hardest, knowing that this would inform whatever measures they took next. But it was a very close call. "We nearly lost her that night," he says. The world's cargo ships, which transport around 90% of global trade, do not always make it to their destination without incident. According to the Safety and Shipping Review by insurance company Allianz, 27 cargo vessels were lost in major incidents during 2021, and 357 during the past decade. They catch fire. They hit rocks, reefs and sand bars. They malfunction. But they don't always sink. Whenever there's a chance to rescue a large ship, their owners almost always take it because these vessels can be worth hundreds of millions of dollars. The people that shipping firms call on in such situations are called salvors. And they have seen some extraordinary things at sea. Salvors came to the aid of the huge Ever Given container ship after she ran aground, blocked the Suez Canal, and triggered global supply chain issues last year, for example. But when a ship weighing tens or hundreds of thousands of tonnes gets stuck somewhere, how do you free it?

Sloane, now a director at Resolve Marine Group, was on his way home from a World Cup match in South Africa when his phone rang and he first heard that the Kota Kado had got into trouble. He flew to Hong Kong the next day. The ship had struck a reef on its way to port, which sliced a hole in her side. Two cargo holds began filling with water and she subsided until she eventually ran into a sediment bank about 25 nautical miles (46km) southwest of her destination. Her bow ploughed into the seabed, trapping her. And as more water flooded on board, the heavily laden ship began to sink. Many were sceptical that she could be rescued at all, remembers Sloane: "A lot of the surveyors said, 'OK, the ship's completely lost, get ready for a wreck removal contract'." But he thought she still had a chance. "She kept on sinking and the bow, literally every day, sank another half-a-metre to a metre (1.6-3.2ft)," he says. "It was touch-and-go."

Sloane and his colleagues came up with a plan to reduce the mass of the vessel and pump as much water out of her as possible. This required lighters – barges, which, in Hong Kong, come equipped with large cranes. Luckily, this is often how cargo is unloaded in Hong Kong anyway, so lots of these barges were available and their operators were already well- accustomed to heaving containers off vessels for transport to shore. Sloane wanted as much cargo removed as possible. In the end, the lighters extricated more than 1,200 individual containers. This sort of operation is time-consuming and difficult, especially given that the Kota Kado was sitting with her bow under water. Plus, the lightest containers tend to be stacked at the top since this helps to lower a ship's centre of gravity and keep her stable – but that means it takes even longer to reach the heavy containers whose removal really makes a difference.

Then there were the giant snorkels. To get water out of the vessel, Sloane and his team deposited large pumps under water at the bottom of one of the cargo holds. They also removed hatches on the deck above and welded huge rectangular tubes, or snorkels, onto them before putting them back in place. The snorkels now dangled down into the belly of the ship. Finally, a team of divers connected the pumps below to two sets of hoses that extended vertically up through the snorkels. The pumps ran flat out, remembers Sloane, to stop water filling the engine room, which contains the most expensive and sensitive machinery. Eventually, having removed huge volumes of water from the hold, the salvage team was able to fill some of the ship's ballast tanks with air in order to refloat her. Had they tried to do this earlier, the tanks could have ruptured, explains Sloane: "When you get below 10m (33ft), you've got to be very careful about how much pressure you introduce." Through all of this complicated work, and in spite of not one but two typhoons, the second of which was particularly bad, the Kota Kado was saved and eventually towed to a shipyard for repairs. She is still sailing today, though under a different name. When ships end up in places they were not really designed for, such as stuck fast in mud or pinned against rocks, the forces of nature can tear them apart. That's why heavy storms presented such a great threat to the Kota Kado. "Like a paperclip, the more times you bend it, eventually it snaps," says Rosalind Blazejczyk, managing partner and naval architect at Solis Marine Consultants. She explains how problematic it is when a grounded ship is lifted or twisted by successive waves. They can crash into it for hours in a swell or high tide, pushing one end of the vessel up and throwing.