I was just wondering about the large waves associated with storms. It seems a little counter-intuitive that large masses of water can be put into motion by moving air (which is much lighter than water). It must take a lot less energy to set a wave oscillating than I am expecting. I'd appreciate an explanation from first principles, though.
This is going to be brief as on a phone : I welcome somebody posting a more complete answer. But the basic principle of large waves appearing from wind is: from a smooth water surface, the wind can produce only small ripples. But those ripples mean that the surface is no longer smooth. The higher the ripples get, the more surface there is for the wind to act upon, thus enlarging them more. Thus are local wind waves formed. For these wind waves to build into the large swell that is found in the oceans, this process needs to continue for a number of days, and some hundreds or thousands of miles. Large swell waves hitting the coast may have been formed in a storm the other side of an ocean.