The term SEA MOTION can be broken down into two crossword solutions: TIDE (4 letters) and SEA (3 letters). TIDE is the regular rise and fall of the ocean's surface caused by the gravitational pull of the moon and sun. This phenomenon is also known as the lunar TIDE or tidal cycle. SEA is a large body of saline water that covers most of the Earth's surface. It is connected to the world's oceans and is home to a variety of marine life.