Free divers hold their breath by using a technique called breath-hold diving. This involves relaxing the body and slowing down the heart rate, which reduces the amount of oxygen that is used. In addition, free divers often dive with a weighted belt, which helps them to sink more quickly. When free divers reach the bottom of their dive, they often exhale slowly, so that they can stay underwater for longer periods of time. When they are ready to return to the surface, they simply take a deep breath and swim back up. This technique allows them to dive for longer periods of time, and reach greater depths than those who do not use this method.