The speed of sound in seawater is about 1,500 m/s (whereas the speed of sound is usually around 330 m/s in air at roughly 101.3 kPa pressure, 1 atmosphere), and varies with water temperature, salinity, and pressure. The thermal conductivity of seawater is 0.6 W/mK at 25 °C and a salinity of 35 g/kg.
The thermal conductivity decreases with increasing salinity and increases with increasing temperature.