you might be making it too cold. i think it really helps after a
marathon to prevent cramping and aid in recovery. it is subjective
like most anything but i think it helped me. i am 70 now so
marathons are not something i can do. one trick
is to get in a warm tub and then gradually cool it. if you do
it a little at a time you can add cold water.
it is similar to jumping in a lake when it is cool outside. if you wade
out slowly and let your upper body cool, gradually your legs
will be warmer than the water or almost the same. diving in then
is not much of an issue as you feel as warm under the water as
outside of it.