When waves travel through water, why do the moving water particles continue to return to their starting position? ?

Waves transfer energy not matter. so simply put, the water doesn't move. it's just being used as a road that energy uses to get from point a to b. it's easier to think of some thing on the water rather than the water it self. like a cork floating on the surface. when a wave passes through the cork. the cork goes up to the peak of the wave and then down to the trough of the wave and then back at equilibrium. it only moved up and down since it was following the wave pattern. if the waves transfered matter as well as energy then the cork would begin to get pushed by the wave and move towards the direction of travel