theloveforphysics
Water has higher specific heat capacity* than that of land(sand) due to which water is heated at slower rate than the land. As the land is heated, the hot air above the land rises up creating low pressure above the land. As the air above water is comparatively cooler than the air above the land , this air moves towards the land due to the pressure difference. This cool breeze blowing towards the land from sea is called sea breeze.
As heating is required for its formation, sea breeze blows during day time.
* Specific heat capacity is the amount of heat required to raise the temperature of unit mass of a substance by 1 K or 1°C.