Ice in sink melted. Did something clog the drain from inside the sink? I'd start looking at it from the sink down to the seacock. If you release the hose on the seacock and if water drains from sink to the hose you are holding (in a bucket or on your shoes) you know the sink drain line is clear. If Clean then you need to examine the seacock and the thru hull. This requires more care than the hose. If no water is coming out the hose, then you have a regular plumbing clog in the line. One last thought, are their any closed valves under the sink for the drain hose between the sink and the seacock?