Thermoclines, or sudden changes in temperature. Where the air temperature is higher than the water temperature, shallow water may be warmed by the air and the sunlight but deeper water remains cold resulting in a lowering of temperature as the diver descends. This temperature change may be concentrated over a small vertical interval, when it is called a thermocline.[3][4]
Where cold, fresh water enters a warmer sea the fresh water may float over the denser saline water, so the temperature rises as the diver descends.[3]
In lakes exposed to geothermal activity, the temperature of the deeper water may be warmer than the surface water. This will usually lead to convection currents.[3]
Context:
The underwater fishing teams picked their spots early. Team Bob went at the mouth of the river, where the freshwater met the salty seawater in the hope that more turbidity from the river and more nutrients will attract more fish. Team Dan went south where they knew there was less of a thermocline, so they could catch fish without taking risks.
Q: Which team was less exposed to extreme water temperature oscillations?