The ship, the Esmerelda, sank in 1503, near the coast of the island of Al-Hallānīyah, which is today part of the country of Oman. The navigational tool is an astrolabe, which the Guinness World Records office has certified as the oldest known such device.

The astrolabe was a circular device that medieval navigators used to find their latitude on Earth relative to the position of the Sun or of stars in the night sky. The found astrolabe, made of a copper alloy, measures just under 7 inches in diameter and sports the Portuguese coat of arms. Commanding the Esmerelda was Portuguese commander Vicente Sodré, a nephew of whom was the famous Vasco Da Gama, the first known European explorer to sail around the southern tip of Africa and then reach India. The ship was one of five commanded by Sodré and his brother, Brüs. Da Gama had reached India in 1498, and other Portuguese explorers followed.

The Sodré brothers were on a mission to patrol southwestern Indian in 1503 when they decided to head to the Gulf of Aden. After they looted a handful of Arab ships, the brothers headed to the island of Al-Hallānīyah to make repairs to their ships. A fierce storm sank two of the ships, which were laden with cargo, and also killed Vicente Sodré. Brüs Sodré died later, of unknown causes.

The ships remained forgotten at the bottom of the sea for hundreds of year. An underwater archaeological survey in 1998 located some signs of wreckage in the area, but unrest in the area prevented further investigation. In 2013, an excavation went ahead. The astrolabe was among the items found the following year.

Among the more than 3,000 items brought to the surface were the astrolabe and a ship's bell with the year 1498 imprinted on it. Researchers said that the bell had been certified by Guiness World Records as oldest ship's bell yet discovered.