On a wooden piling in the waters off Brooklyn Bridge Park, a lone red fruit grows between Pier 1, right next to the Brooklyn Bridge, and Pier 2. Sure, it’s tomato season, but this one seems to have materialized without the aid of any planter or gardener.

“I saw the yellow blossoms and paddled over to it,” said Matthew Frey, a kayaker who discovered the rogue tomato on Monday while kneeling on a paddleboard. He tried to hold steady enough to take a picture on his iPhone.

“I’m used to seeing things grow here, but nothing as special as that,” said Mr. Frey, 54, a board member at the Brooklyn Bridge Park Boat House. “Things like that just make me happy.”

Other pilings — those that poke above the East River waterline, that is — also sport plants. There are a few tufts of green, a few of red, weeds growing out of reach from the estuary’s saltwater. But there’s nothing like the tomato.