Why do winds changes during the day and night near a beach?

Land absorbs heat from the sun much faster than the water. Then the warm air over the land rises and the cool air from over the water rushes in to replace it. Sea breeze, caused by convection. The warmer air is less dense. At night, the water cools much more slowly than the land. The warmer air over the water rises and the cooler air from over the land forms the land breeze.