Deming,
In the user manual for Ver 6.04, section 5.1.11.1 it explains how to adjust the temperature offset.
Manuals can be downloaded from the LXNAV website he
https://gliding.lxnav.com/lxdownloads/manuals/
I'm also not sure that putting the probe in water was a good thing as I believe there is a small current that runs through the probe and getting it wet may not be good.