It's, well...the beach was covered in trash like that at one point, too. From what I knew about it, it was just...pollution. Really bad pollution, over a long time.

[Izuku is pretty sure the beach had been just being used as a straight up dump for a while by people...he shakes his head slightly.]

But the way it is now, it's since been cleaned up. I don't know where more trash other than what's already there could be coming from...