Depending on what you normally ride, short or longboards, then that’s what you’ll need most of the time in Irish waves. The surf is powerful but you can pick and choose what you go out in so it suits your ability and the quiver you own.
If you want to use an Irish surf trip to step up your performance levels a bit though then it’s wise to take a step up board. Something with a little more length known as a semi gun. So if you ride a 6’2 normally that would be a 6’6 or a 6’8.