The color of light that does not penetrate 70 meters beneath the ocean surface is red.

Here's why:

* Water absorbs different wavelengths of light at different rates.

* Red light has the longest wavelength of visible light. This means it is absorbed most readily by water molecules.

* As you descend deeper into the ocean, red light is absorbed first. By the time you reach about 70 meters, almost all red light has been absorbed.

This is why the ocean appears blue! Blue light has the shortest wavelength and is absorbed the least, allowing it to travel further in water.