Here's why:

* During the day: Land heats up faster than water. This creates a low-pressure area over the land, while the cooler water has higher pressure. Air flows from high pressure to low pressure, resulting in a sea breeze.

* At night: The land cools down faster than the water. Now, the water retains more heat, becoming the low-pressure area. The air above the land, being cooler and therefore higher pressure, flows towards the sea. This is the land breeze.

In simpler terms, the land breeze is a result of thermal differences between the land and the sea, with the cooler land air flowing towards the warmer sea air at night.