Waves are beautiful to look at, but they can destroy ships at sea, (11) houses and buildings near the shore. 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 wind to blow. The winds blow across the sea, pushing little waves into bigger and bigger ones. The size of a wave (13) how strong the wind is, how long it brows, and how large the (14) of water is. In a small bay, waves will never build up. But at sea, the wind can build up (15) powerful waves.