Technical problems have been blamed after ferry services between Dublin and Holyhead were disrupted.
Stena Line said issues with one of its vessels, the Stena Adventurer, had developed a fault which needed to be resolved before it can leave Holyhead port.
Irish Ferries said its 11am Ulysees sailing from Dublin on Sunday morning was unable to berth, leading to later ferries being cancelled or delayed.
The disruption has affected Welsh rugby fans returning home following Friday night's Six Nations defeat against Ireland.
A Stena Line ferry leaving Dublin at 10.15am will be diverted to Birkenhead with foot passengers being taken by coach to Holyhead.
A spokesperson said the port operators were working hard to resolve the technical issue and advised passengers to check before they travel.
They added: "Our team is on hand to support passengers, including the provision of coach travel back to Holyhead for foot passengers."
"Our team is contacting affected customers directly with updates, changes and alternative travel options."
Disruption on Irish Ferries services has also stretched into a second day - with the 1.30am Ulysees sailing from Holyhead delayed by ten hours.
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