A sperm whale cracked the hull of a yacht sailing in the remote South Pacific, forcing four crew members into an 18-hour fight for survival on the high seas.

The crew of the 16-metre (52-foot) Tai Tam told AFP on Thursday of their weekend collision with a pod of sperm whales roughly 250 nautical miles north of Norfolk Island.

Australian Jemma Cooper, at the helm, said a loud thud pushed the boat sideways and threw her from the steering wheel. She noticed a brown discolouration in the water, then spotted a sperm whale.

“We looked out to our port side and there were six to eight, a pod, of whales there. So then it became clear that that’s what it was,” she said.

Her husband, Jeremy Cooper, sleeping below deck, was woken by the impact. “It was pretty immediately evident it was very serious,” he said. “All the steering gear was smashed on the starboard side and there was a significant amount of water coming in.”

About 30 minutes after the collision, at 13:00 New Zealand time on Saturday, the crew activated an emergency beacon and declared a full mayday. New Zealand crew member Terry Hetherington said they spent the next several hours bailing water.

The Royal New Zealand Air Force flew a P-8A Poseidon patrol plane to the area to establish radio communications and coordinate the rescue.

French crew member Martin Jaffre, a joiner, said the collision left several gashes in the hull, cracked the fibreglass structure and broke the steering. “We could no longer steer the boat and a boat with no steering quickly becomes a problem,” he said. Jaffre used expansion foam to slow the flooding and swam below the boat to inspect the hull, his crewmates said.

The sailors bailed water by hand and fought to keep the engine from clogging for as long as possible. Late at night, they abandoned the yacht for a life raft in calm seas under a full moon. In the early hours of Sunday, they cut the tether to the vessel, fearing it would drag them under. It sank shortly after.

The 143-metre container ship MV Sofrana Surville rescued the four sailors at 06:00 on Sunday – about 18 hours after the whale strike – the New Zealand military said.

Jeremy Cooper said the rescue itself was frightening as the giant ship bore down on their tiny raft, but within half an hour they had climbed a ladder aboard, had coffee and spoke with the captain.

“It was wonderful, wonderful, and just a terrible, terrible ending – but luckily no loss of life,” he said.

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