There is a site off Palos Verdes California I call Golf Ball Reef. There are dozens of golf balls along the edge of the reef nearly 3/4 mile from shore. I have no idea how they got there.
Plate tectonics. I am a bit surprised that there isn't any evidence of the dust layer from the dinosaur killer off the Yucatan. Although, if the crabs have been cleaning them off this whole time........................