Stena Line has revealed that it carried an additional 5,000 passengers on its Belfast to Stranraer route in the latter part of this month.
The significant increase in passenger numbers was attributed to continued flight cancellations and airport closures due to wintry conditions.
Stena Line said all its Ireland ferries and UK sailings are operating as scheduled and that the company has brought in extra staff and additional coaches to help deal with the extra demand.
Nigel Tilson, communications manager at Stena Line, said sailings - especially UK ferries - are continuing to book up fast so people are advised not to leave their travel arrangements until the last minute.
"We recommend customers book their ferry crossing through the website or our call centre rather than arrive at the port without a booking as they may face disappointment," he said.
Around 15.4 million passengers travelled with Stena Line during 2009, while 3.3 million cars and 1.6 million freight units were transported during the same period.
Written by Andrew Smith