Only a very small amount of solar heat radiation penetrates more than three feet (90 cm) below the surface.

"We're also taking water from the bullet holes that penetrated below the waterline."

Nor did they see the bomb strike the volcano's slope above the Odyssey facility and penetrate deep below the surface.

How many ages that planet must have frozen for the cold to penetrate so far below the surface!

"So long as the river can't penetrate below the waterline, we stay afloat."

Nor do they mention that it penetrated below the first level in the landing site.

At the original landing site, they penetrated several miles below the surface before they could proceed no further, but not here.

On 27 April, a small caliber shell penetrated a fuel oil tank five feet below the waterline.

The Deep Space 2 impactor probe was to be the first spacecraft to penetrate below the surface of another planet.

Most stains on a vinyl floor do not penetrate below the surface.