Irish Ferries has cancelled some of its services between Holyhead and Dublin due to a technical fault.
The MV Ulysees has been taken out of action for repairs because of a problem involving a propeller shaft.
A spokesperson for the company said it expected the ship to resume service by the middle of next week. All passengers affected by the cancelled services will be accommodated on alternative ferries.
Irish Ferries is also organising extra services this weekend involving the Epsilon ferry, which usually runs from Dublin to Cherbourg. Passengers are advised to check schedules for any changes to service times.
For more information, call the Irish Ferries office at Holyhead Port on 08717 300 200 or the contact centre during office hours on 08717 300 400.