a normal skintone is one shipped by Maxis or one that uses the Maxis default nude meshes; "shower-proof" skintones have been modified by a very clever hacking (discovered by the lovely Marvine - all praise her name eternally) that use custom meshes.
Amen to that, and thanks for the very good explanation. Also many many thanks for the meshes - finally a small counterweight to all those cupDDDD meshes! Now I can just get as dirty-minded about my sims as 15 year old boys. Oh joy.:blob6: