A trip from London to Auckland on jetskis has been called off.
The New Zealand-led team got as far as the south coast of Turkey before cancelling the mission because of equipment problems, the threat from terrorism and a lack of money.
Writing in his blog, team leader Jeremy Burfoot says a leaking fuel tank would have made long ocean crossings impossible.
Mr Burfoot says the risk of terrorist and pirate attacks in Yemen has risen to an unacceptable level and his team would have been a prime target.
The decision to cancel was also worked out with the team's main sponsor, he says.