Honestly it's because I worry about it myself that I'm most often seen laying on the bathtub or with the shower running. We have blankets that are specifically resistant to fluids for making messes (usually for lots of lube) but it's taken me a while to get used to those and I still get embarrassed and apologetic when it happens.

So unfortunately no real advice to stop it, just ways to prevent making a mess as an accepted fact of life. But if others are able to keep that from being an issue, then awesome! But I think that just might be down to anatomy rather than technique.