Upvote:2
I travelled westbound with Stena Line and eastbound with Irish Ferries in 2017, between Holyhead and Dublin. I was a foot passenger with a bicycle. Westbound, I had to check in my bicycle. I don't know if there was a scan after check in. Eastbound, I rode my bicycle + luggage onto the ferry with the cars. Either way, none of the luggage I carried on-board was scanned, but when I arrived as a foot passenger there were some officials who could have stopped people for a check, but didn't.
Incidentally, in neither direction did anybody ask me to identify myself at any moment.