The thermodynamic properties of seawater have recently been redefined as the International Thermodynamic Equation of Seawater—2010 (TEOS-10 for short), and here we summarize the changes to oceanographic practices that are needed to take advantage of this new international standard. A key feature of TEOS-10 is that the thermodynamic quantities are functions of a new salinity variable, Absolute Salinity, which incorporates the effects of spatial differences in seawater composition. TEOS-10 also treats the “heat content” of seawater in a more consistent and natural fashion through the introduction of a new temperature variable, Conservative Temperature, which replaces potential temperature. Since TEOS-10 includes fundamental equations of state also for ice and for humid air, thermodynamically consistent and complete relationships now exist between all the thermodynamic properties of fresh water, seawater, ice and humid air.