I would first measure the temperature of the water then measure the temperature of the water AFTER the sun go down .
It's a system of chronological dating and geologists use it to describe the timing and relationships of events in Earth's history
This is true that the pressure in the mesosphere is so low that a person could not be in this layer without a spacesuit.
The mesosphere is the region of the earth's atmosphere which is above the stratosphere and below the thermosphere. It has a very low temperature and pressure. The top of the mesosphere is the coldest part of Earth's atmosphere.
Yhe phase you are describing is the lag phase.
