why does not light reach very deep near the ocean floor?

Question

light can travel millions of kilometres through outer space, but the deep ocean with a depth of more than 2000m is often pitch black. suggest why?

Answer 1

You already gave the answer, in empty space light can travel endlessly, in air it's diffused by the molecules (hence the blue sky), in water a lot more since water is a much denser than air.

Answer 2

In space, there is only a little matter to interfere with light, so we can see light from stars hundreds of light years away.

Water diffracts light, causing it to split and bounce in several directions. As you go deeper, the water is diffracted more, because as you go deeper, the water is more dense. When you get to the really low depths, the amount of light getting through is miniscule at best.

Answer 3

There is this stuff called water in the way. Ocean water is not clear. It has a whole lot of suspended material, such as minerals, plankton, fish, fish droppings, etc, that all cast shadows as the light hits their topsides. It all combines into one huge shadow that blocks all light from the bottom.