in a lake there can be many vehicles that travel to get from point a to point b. what then occurs in this is rippling waves as a boat passes. usually a lake would be pretty still yet vehicles disrupt current as well as wind speed. what occurs is called waves and these waves travel through a medium. for instance if a fairly big wave comes along I myself move along with the wave along the medium thus forcing me up then back down. these waves that occur tend to be transverse. the opposite is longitudinal and tends to be sound waves and these waves vibrate objects in a medium instead of forcing an object through a physical wave.