It may be an idea to e-mail Bayer, they responded quickly when I queried Chaz's lungworm, gave good advice, and followed the treatment through with our vet.
As with all spot on treatments the active ingredients are absorbed through the skin into the bloodstream so I can't really see how bathing or swimming can cause them to leach back out of the body. It's probably an indication of how long it takes for an effective dose to be absorbed before the remainder, lying on the skin surface, can be safely washed off. Our groomer and vet both tell us to leave two days between applying Advocate and bathing our furry ones and, despite trips to Aberdeen beach for a dip in the north sea, paddling and swimming in the river dee and the baths and showers to remove mud, salt and all other smellies that cockers seem to love, we've not had one flea appear since using Advocate. Over the time we've had cockers we've removed about a half dozen ticks but they're always checked after walks as there is quite a deer population in the area.
Just my non-expert view but I'd certainly advise contacting the makers for further advice.
Bob.
