What is the point at which a sudden change in water temperature occurs called?

The term for the point at which a sudden change in water temperature occurs is called a thermocline. This layer in a body of water separates warmer surface water from the cooler depths below. The thermocline is important for divers as it can affect buoyancy, visibility, and marine life behavior. In regions where thermoclines are present, divers may experience a noticeable shift in temperature as they descend, which can also impact their thermal comfort.

Other terms provided have different meanings. Thermohaline refers to variations in water density caused by temperature and salinity differences, influencing ocean circulation. A temperature gradient describes the rate of temperature change in a given area but does not specifically refer to the distinct layer. An isotherm is a line on a map connecting points of equal temperature, primarily used in meteorology rather than in the context of water layering.