Cold Bottom?

[finin]

I have been messaged a few times asking how i know how cold the bottom is, maybe some think im bs'n when i say its its 21 up top and 16 on the bottom.       Heres what i use, a thermo gun. Point it at the sinker and it reads the temp. I also use it to check and calibrate my sounder temp.

[JonD]

I use my dive computer, but you also visually see temp changes in he water. Often rising up just 1m can make a huge difference.