Green’s Dictionary of Slang

used in sex contact advertisements, urolagnia.

1986–7		Maledicta IX 159: Now we must turn to the piddling nuisances of what is often called W/S (water sports or the erotic games of golden shower queens with urine).
2005		small-ad in E. White My Lives 122: VGL XXX horny dominant top WS, FF, C&B torture, BB, verbal.