The skintone meshes you do have may not include shower-proof versions.
See here:
http://www.insimenator.org/showpost.php?p=597584&postcount=7There are many different shower-proof skintones for both the HBB and the SBB.
Some basic ones are here:
http://www.insimenator.org/showthread.php?t=19759http://www.insimenator.org/showthread.php?t=41146