The National Sleep Foundation claims that there have been studies made where researchers found that people who soaked in hot water before bed would have better amounts of deep sleep. Additionally, the Associated Professional Sleep Societies Journal claims that soaking for an hour and a half will allow you to fall and stay asleep a lot easier. This is possible because the body goes into hibernation by lowering the body temperature. The heat of the hot water will force your body to lower its temperature as well, and therefore force it to feel sleepier.