What Charles Moore discovered in the Pacific Ocean in the late 1990s is what is now called the Great Pacific Garbage Patch. This is a very large area in the northern Pacific Ocean (larger than the state of Texas) that is filled with floating garbage.
Moore’s discovery has gained a great deal of attention in the public eye. It shows the degree to which people in the world have polluted the oceans through carelessness and through the creation of the “throwaway society” that you asked about in a previous question. The fact that enough garbage gets into the ocean (which is not even our main place of dumping garbage) to create such a huge garbage patch shows that we are throwing away massive amounts of garbage. This can be seen as an indicator of our general lack of concern about environmental issues in general.