Jim you are unfortunately full of shit. How unusual. Do you know what a passenger manifest is, and what it is used for?
"Irish Ferries recommend all passengers bring a passport with them. Irish and British citizens do not strictly require a passport to travel between the two countries - some form of identification is however required. Please note that all nationalities except Irish or British require passports."

"Ireland, along with the UK, is a member of the Common Travel Area. British nationals travelling from the UK don't need a passport to visit Ireland. However, Irish immigration officers will check the ID of all passengers arriving by air from the UK and may ask for proof of nationality, particularly if you were born outside the UK."