Freeze desalination of seawater using direct contact freezing and melting heat transfer has long been known to be very energy efficient. However, practical difficulties and developmental mishaps have blocked commercial success. The unsuitability of conventional refrigerant compressors for use in freeze desalination plants has been a major obstacle. The recent invention and development of the hydraulic refrigerant compressor now provides an excellent solution to the compressor problem, and the advantages are such as to make reconsideration of freeze desalination worthwhile. Herein suitable candidates are described for each of the principal system components including the hydraulic refrigerant compressors, and the characteristics of a resulting freeze desalination system are discussed.