The sensation of weightlessness cannot be duplicated in a sensory
deprivation tank. It simply is not the same. The sensation of your
balls rising into your abdominal cavity is perceived all the way down
from the ten meter tower (the "high board" is only three meters). It
is not a transient effect. (I do hope that some other male in this
group has had the same experience I have in this regard. I thought it
must be common.) One difference you will note between floating and
freely falling is that you always know (proprioceptively) which way
is up while floating; you don't while freely falling.