Extra Swift sailings over the weekend, as expected, departing Dublin at 20:30 arriving back from Holyhead at 01:40 first sailing at this time on Friday. Also noted that no new bookings are being taken for some sailings on Dublin-Holyhead route, this quote from IF.
"Due to a technical issue with our cruise ferry Ulysses, some sailings on the Dublin to Holyhead route are currently not accepting new bookings. If you have an existing booking and wish to amend it, please call us. Passengers on affected Ulysses sailings are currently being contacted and offered an alternative sailing. Please be patient. We apologise for this inconvenience."