There has been some discussion and debate on here about the quality of the ships water. I personally don't like it. I do brush my teeth with it and drink tea and use the ice from food service. But that is it for me. I can be pretty sure about telling you that it does not come out cold.
I would get one of the buckets they serve the buckets of beer in. You can get from lido bartenders or room service, or just ask your steward. Put yourself a nice bottle of water in it, and they will keep it ice cold for you.
Why ruin your Scotch?
Best to you,