The ocean is covered by sea ice for at least 15 percentage some part of the year. Like fresh water, ocean water also freezes, but at lower temperatures. Fresh water freezes at 32 degrees Fahrenheit but sea water freezes at about 28.4 degrees Fahrenheit, because of the salt in it. Given here the online calculator to calculate freezing point of ocean water. Ocean water freezing point calculation is done based on the salinity and pressure.