But quick-thinking four-man team of Stuart Shepherd, Martin Skehan and brothers Gary and Stuart Richards have used a sandwich-box lid to plug the leak.
“There was no Mayday signal and they were all trained in how to deal with it,” said Amy Shepherd, Stuart’s daughter.
“They tried black marine glue but that didn’t work, so they have used a sandwich box lid to plug the hole.”
Amy, who spoke to her dad at midday on Monday said the boat has taken on about 70 litres of water, the equivalent of a whole extra person. At midday on Monday they were 790 miles away from Antigua and the incident could add an extra day or two on to their journey.
“They want to finish,” said Amy. “If they take any help from the safety boat it will count as an assisted finish and they don’t want that.”
They had been hoping to finish the 3,000 cross-Atlantic trip on January 19 or 20.
Organisers at the Talisker Whisky Atlantic Challenge said: “At 13:47 yesterday the safety team were contacted by fours team Wrekin Rowers to report that they had experienced a strike by a marlin that had pierced through the hull and into the deck.
“All crew members were safe and no injuries were sustained. After working through a number of temporary fixes with the safety officer on duty, the crew are battling forward towards Antigua.”
They added: “They have done the best they can to repair it for now, but with the extra weight of water on board, it is likely to slow them down significantly.
"This is a real knock back for the team as they’re so close to the end, but we’re just thankful they’re all ok and reminding them that it is about completing the race, not the position that they finish in. They have done the best they can to repair it for now, but with the extra weight of water on board, it is likely to slow them down significantly.”
They added: “Although their row has changed slightly now, the team are cohesive and as strong as ever with even more incredible tales to share when they get safely to Antigua.”
They had been hoping to finish on January 19 or 20 but that is likely to be delayed.
The team, from Wellington, was taught how to cope with marlin strikes before they started their journey.
So far they have raised more then £79,000, with the final total to be split between the RNIB and Severn Hospice. They are aiming to raise £100,000.
Donations can be made at www.wrekin-rowers.com/donate.