Regardless of what people say,,, soaking is NOT a good thing. Usually adjustments in temp and humidity are a factor. There is also the possibility of mites.
Anybody can argue this, but on the boa constrictor front, Gus Rentfro, who is next to God when it comes to boas states that prolonged soaking is a sign that something is off. It can also lead to problems due to too much moisture when a snake constantly stays in a water dish. He does not give his boas giant water dishes to soak in.
In relation to royals, the "open savannas" where these animals typically rage, are not swampy, or puddled with standing water.
In my own experience, I have never had any of my 3 snakes. royal, boa constrictor or carpet python do anything but drink from their water bowl.
Before anybody get's all defensive here, note that I say prolonged use. We all have snakes with quirks and little things that make them individual.
Even still, keep a close eye on any snake other than a water dwelling species that is constantly in water.