Cook's crew sealed a sinking ship's hole by fothering a sail

On 11 June 1770, HMS Endeavour struck what is now called Endeavour Reef on Australia's Great Barrier Reef, tearing open the hull below the waterline and taking on water faster than the ship's pumps could clear it. The breach was below the waterline and largely inaccessible from inside the hull, and there was no way for the crew to reach it directly to nail on a conventional patch while the ship was still afloat and taking on water.

Fighting the flooding with pumps alone bought time but didn't address the hole itself, and any patch applied from inside would have had to fight the same water pressure driving the flood in the first place. What the crew needed was a way to seal the breach from outside the hull, using a method that didn't require anyone to work inside a flooding compartment or physically hold a patch against pressure strong enough to sink the ship.

Using a technique called fothering, Cook's crew took a spare sail, worked oakum, wool and manure into its fibers, and hauled it under the ship's hull on ropes until it settled over the breach. Rather than fighting the water pressure driving the flood, the technique used that same pressure to hold the sail firmly against the hole from outside, sharply slowing the inflow.

They packed a sail with oakum, wool and manure, hauled it under the hull, and let the water pressure driving the flood press it against the hole from outside.

The breach was below waterline and unreachable from inside, so conventional patching was impossible.

Water pressure drove the flood, but from outside that same pressure pressed the sail against the hole.

The sail's flexibility let it conform to the irregular breach, creating a seal.

The pressure differential held the patch in place without needing crew to brace it, buying time to reach shore.

Redirect the damaging force to hold your fix in place instead of fighting it head-on.

The fix held long enough for Endeavour to be sailed to the mouth of what is now the Endeavour River, where the crew beached the ship and carried out more thorough repairs lasting until early August 1770 before continuing the voyage. The Endeavour Reef fothering remains the most cited historical example of the technique in maritime history, and fothering itself is documented as a standard emergency method used elsewhere at sea for centuries — a textbook case of using the very force causing a failure to help hold its own fix in place.