What do we know about sea Most of us have seen it. Many of us have swum in it. We know that it looks very pretty when the sun is shining on it. And we also know that the sea is full of waves. Waves are beautiful to look at, but they can (11) ships at sea, as well as houses and buildings near the shore. What causes waves Most waves are caused by winds blowing over the (12) of the water. The sun heats the earth, causing the air to rise and the winds to blow. The winds blow across the sea, pushing little waves into enormous ones. When the wind is blowing at 120 (13) per hour, most waves will be about 12 meters high. In 1933 the United States (14) the largest measured wave in history. It rose in the Pacific Ocean to a (15) of 34 meters.