Sentence:  An extended cold spell caused ice to build up on the aerator which was mounted on a floating platform and caused the entire platform to sink lower in the <WSD>water</WSD> . 
Meaning of the word marked with <WSD> tags:  binary compound that occurs at room temperature as a clear colorless odorless tasteless liquid; freezes into ice below 0 degrees centigrade and boils above 100 degrees centigrade; widely used as a solvent