That moment after you jump in the pool but before your genitals get adjusted to the cold water. Also for sitting down in a very hot tub.
1 - As Jimmy jumped in the pool, a thermal crotch transition occurred, and he yelled, "Ahhh my krundle!"
2 - As Jimmy sat down quickly in the hot tub, a thermal crotch transition occurred, and he yelled, "Ahh my krundle!"