Esther Greenwood, the protagonist of The Bell Jar challenges her friend Cal to swim out to this rock with her during Chapter 13:
“I lifted my head and squinted out at the bright blue plate of the sea-a bright blue plate with a dirty rim. A big round gray rock, like the upper half of an egg, poked out of the water about a mile from the stony headland”
It can be found to the left of the causeway leading out from Lynn to Nahant.
“I heard the sand thud behind me, and Cal came up. “Let’s swim to that rock out there.” I pointed at it.
“Are you crazy? That’s a mile out.”
“What are you?” I said. “Chicken? “
During the day in the summer, plan to pay to get on the beach. It’s free in the evenings—or if you park on the mainland and walk.