What is most likely to cause someone to fall overboard?

Moving around the boat while underway significantly increases the likelihood of falling overboard. When the boat is in motion, especially in choppy or turbulent waters, the balance of the vessel can be compromised. Shifting your weight as you walk or change position can lead to a loss of stability, making it easier to slip and fall overboard. This is particularly true for smaller boats or those that are not equipped with high sides, where a sudden movement can easily result in an accident.

Other factors, like weather changes or throwing items overboard, can contribute to hazards while boating, but they do not directly lead to a person falling overboard as much as moving around the boat does. Holding onto the boat's sides is a safety measure that people often use to stabilize themselves, while throwing items overboard may create distractions but does not pose a direct risk of falling. Therefore, the most critical factor here is the act of moving around in an unstable environment, which is why it is essential to maintain balance and be cautious when onboard a moving vessel.