Hidden among the grass flats off Conch Key are two low mounds of round ballast stones that mark the place where Nuestra Señora del Rosario Santo Domingo, San Antonio y San Vincente Ferrer grounded on July 15, 1733 during a hurricane. This merchant ship, commonly called Sueco de Arizón (the Swede of Arizón) for her captain Juan José de Arizón and owner Jacinto Arizón, may have been built in Sweden as her nickname suggests. Sailing in the rear of the flota near Almiranta, Sueco must have been one of the smaller vessels since she was carried by the storm into only nine feet of water. Her hull remained intact, although she lost masts and rudder. No lives were lost and her cargo (silver, porcelain, leather hides, cochineal, indigo, and tobacco) was saved.
Although no traces of the ship's hull are visible today, the wrecksite is home to hard and soft corals, sea fans, brittle stars, crabs, and schools of juvenile angelfish, wrasses, and drums, which live among the ship's ballast stones. The two mounds of river rock represent an initial grounding spot and a later deposit of ballast as the hull eventually deteriorated in the shallow water. Exploring the seagrass, snorkelers can follow a scattered ballast trail almost to the shore of Conch Key.