One intrepid traveller has made the journey at least 16 times this year, lured by the theme- night disco, casino, cabaret, cinema, sauna, Jacuzzi, bars and restaurants. The Dyfed port simply cannot compete.
A day ticket costs pounds 8 for the 10 1/2 hour round trip and the company has had to limit numbers to 300 to make sure there is room for conventional holidaymakers. In winter, when the sea has been rough enough to prevent the dance troupe from performing, day-trippers have made up the bulk of the passengers.
The Stena Hibernia, previously used by a Scandinavian line for Baltic cruises, is large enough for holidaymakers who want to avoid the revelry to find sanctuary elsewhere. But taking a slice of Welsh nightlife on to the waves is not without its problems. Tony Wilkins, the ship's food and beverage manager, said: 'We see a lot of them a little bit merry and we don't mind them singing. It's when they start to fight that our worries begin.' When the fights do begin, hefty security guards are on hand to nip them in the bud. The only fight I saw came when a member of a skittles team tried to chat up somebody else's wife. The ship does boast one unusual facility: a jail with three cells, so that if revellers go over the top they can be put in secure accommodation.
An alternative tradition is also catered for. When the ship sails, few of its cabins are booked. But staff are used to a steady trade as the night slips by and couples decide to cement friendships struck up on the dance floor.
On docking at Rosslare, there is less than two hours to see the sights before it is back on the boat and home. The Irish locals are used to the flying visits. One man taking a break from walking his dog said: 'We don't mind them coming at all. They just head to the nearest bar and drink. Sometimes they start to become a nuisance but they are only here a short while.' He recommended a bar far from the ferry terminal, which the trippers rarely reach.
Back on board, it is time for the cabaret. For the singer, Adam Starr, performing for drunken day-trippers may not be the pinnacle of his career but he gets an enthusiastic reception, with several women trying to scale the stage to dance with him.
A member of a skittles team reflects on a good trip. 'Last year we had our social at the Bath and West Agricultural Show. This is a hell of an improvement - the beer has been flowing all day.'
Idy Edroo, manager of a Cardiff football club with a regular fixture in Kilkenny, said his team had always flown until they tried the ferry. His verdict: 'It's better than a nightclub - and then there's the duty-free.'