During the day, the sun's radiation heats the land more rapidly than the water. The land transfers this heat to the air directly above it through conduction. This warmed air becomes lighter and less dense, causing it to rise. As this warm air rises, cooler, denser air from over the sea moves in towards the land to replace it. This continuous cycle of warm air rising and cool air moving in creates a convection current, which we experience as a sea breeze.