Three crew members were injured and 41 cars damaged when a ferry met high winds crossing from Weymouth to Jersey in what one passenger called: "the voyage from hell."
The Condor Vitesse left Weymouth at about 1.15pm on Sunday afternoon.
Captain Fran Collins, from Condor Ferries, said wave heights had stayed within safe limits throughout the journey. However, she said unexpectedly high waves around the Casquets Lighthouse caused problems despite the ship slowing down.
Adam Spur, who was on the crossing, said many passengers were sick.
"We could hear bits-and-pieces in duty free falling about and smashing... and from what I understand, pretty much every car on board had gone into the car next to it," he said.
Captain Collins, ports and guest services director at Condor Ferries, said the vessel set sail "clearly within safe operating limits. The majority of the sailing passed without incident. However, near the Casquets, wave heights unexpectedly increased, causing the journey to become very uncomfortable. As a result of this, three crew members were hurt, none of them seriously, and 41 vehicles were damaged. There were 112 cars and 400 passengers on board.
"The departure from Jersey to Weymouth was delayed for two and a half hours to wait for more comfortable weather conditions. The ship was routed up the eastern coast of Jersey en-route to Guernsey for the comfort of guests.
"Condor Ferries places the safety of its passengers and crew above all other considerations, which means that our ferries only ever sail within the safe limits which are set by external agencies."