Water Safety Instructor (WSI) Practice Exam

Buoyancy refers to the upward force exerted by a fluid that opposes the weight of an object immersed in it. This force is what keeps an object, such as a swimmer, afloat in water. When the force of buoyancy is greater than the weight of the object, that object will float; when it is less, the object will sink. Thus, stating that buoyancy is the force keeping a swimmer afloat accurately captures this fundamental principle of physics. In contrast, while displacement of water is related to buoyancy, the term specifically indicates the weight of the water displaced rather than the force itself. The energy used to swim fast relates to the swimmer's exertion and efficiency in water rather than the concept of buoyancy. Likewise, the resistance felt in water pertains to drag and does not pertain to buoyancy directly, even though both concepts are involved in swimming dynamics. Thus, the correct identification of buoyancy as the force keeping a swimmer afloat highlights its key role in determining the ability to stay buoyant in water.