It’s mating season for the Horseshoe Crabs at Hemenway Landing. You could see a lot of them along the edge of the water. (Click on blog link for other photo.)
“The crabs live in the ocean year-round but come ashore like clockwork every year between the May and June full moons to mate and lay eggs.” The ones that I saw looked pretty old with lots of seaweed and barnacles growing on their shells.