Assuming the temperatures, humidity and other husbandry issues are fine...He will be fine, snakes can soak, and even swim. It might just be a shedding thing. or maybe he is trying to kill mites. check in the water bowl after he has soaked for a long time to see if there are little dead mites that look like poppy seeds.
Could he be overheating? What are the temps? Is it too dry? What is the humidity?