. . . If we’d tried to come by car, we wouldn’t have been allowed to park until after five without a beach sticker. But arriving by boat, the dreamlike Lambert’s Cove and its sandy beach are ours. Brad sets up a halyard on the bow, and we swing on the line like Tarzan, soaring into air so soft that it feels like fur. And then, one by one, we fall into the warm water and linger there. Back on the boat, we change our minds about dinner again: The Blue Whale is too good to leave, and everyone has arrived with food. Instead of a beach picnic, we have a loud and rather raucous feast of smoked mussels and sushi from Martha’s Vineyard, smoked bluefish and bread from Nantucket, cheese from Chatham, and ripe tomatoes, cucumbers, and basil from my garden. Our towels and swimsuits, pinned to the railing of the boat, flap in the balmy night air.