The sun warms the Earth. Its rays cannot reach all the way to the bottom of the ocean, and it certainly stops warming the water at a certain distance.
The opposite of bottom would be the top, so the oceans surface is the opposite of the ocean floor/bottom.
This section of the ocean from floor to surface is called the water column.
Earth's crust is composed of the continents and the ocean floor.
The ocean's surface
The ocean is 71% of the Earth's Surface.
oceans and seas
Surface zone
The temperature of the ocean at the surface is not constant across all oceans. For example, the Arctic Ocean will have a much colder surface temperature than the Pacific.
Plankton
Oceans are seawater throughout, not only on the surface.
Wind causing waves are formed at the surface of the oceans.
The cooler saltier water sinks toward the ocean floor.