I just take a good flask onto the ferry. We normally have a few drinks in one of the bars. Before settling down for the night in our cabin, I go back to the bar with the flask and for the price of a cup of tea, they give me a teabag and fill the flask with boiling water. It's still scorching hot in the morning, so we have a nice cup of tea before going for breakfast. We both drink tea without milk which helps.