I grew up less than 5 miles from there, spent a good part of my childhood exploring that beach. So many bottles, but also construction waste, lots of old tile and metal fixtures, and most surprisingly lots of old bones. At one point there were rendering plants that would process the carcasses of the thousands of horses and other animals that would die across NYC every year. After processing, the bones would just be dumped in the water. Not sure if it was official or just a local name, but the area became known as Dead Horse Bay.