Background Paragraph: 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]. 
Story: Deep lake presents geothermal activity, while Shallow lake has mixing of saline water with fresh water. Deep lake had more instances of divers having problems because of thermoclines.
Which lake has colder water the bottom? Which lake has fewer thermoclines? Which lake has less geothermal activity? Which lake has less water salinity? Which lake has more geothermal activity? Which lake has more thermoclines? Which lake has more water salinity? Which lake has warmer water the bottom? Which lake was less dangerous to divers? Which lake was more dangerous to divers?