It is safer that way.
close to the surface
because they want to swim close to the surface
The gravitational pull keeps the Earth's atmosphere close to the surface...
The air is close to the surface of the earth because gravity holds it there
depends. how close do you mean. Because technically everything in the cell is close to the surface because of how small it is.
A medical term that means at or close to the surface is superficial.
The forks should be as close to the ground as possible.
surface soil
The forks should be as close to the ground as possible.
The scientific name for veins that are close to the surface is superficial veins. These are the veins you can see under your skin.
Mostly for the same reason you stay close to the surface of the planet - gravity!
a cloud can be close to the surface of the water (or land). When a cloud is close to or at the surface of the water (or land) , it is called fog.