28 degrees Fahrenheit, the temperature of the North Atlantic on the night the Titanic sank.
It was about 45 degrees
I don't know exactly, but you could make an educated guess... It was cold enough for there to be a big iceberg in salt water. So I think if you find out the temperature at which sea water freezes you will have the answer, assuming the temperature to be just above that (if it were the actual freezing point of sea water the Titanic would have been trying to go through a sea of ice, and it wasn't, was it?).