Rusty ball on the rocks
It that a wrecking ball? Wrecking balls are heavy. How could one wash up on shore? Maybe I've just never been in the park at a time when nature would let me notice this; the tide was very low when I arrived. Or maybe this is an old buoy. It probably is, right? That would make more sense – it would be light enough to wash up somewhere and it would belong near the water because it likely was in the water before the beaching.
I don't know that I know what either a buoy or wrecking ball actually should look like.