The last section of the museum, which opened on 7 June 2008, is dedicated to one of the most important underwater discoveries of recent decades, a shipwreck in the stretch of sea between the coast of Sinis and the island of Mal di Ventre that occurred during the 1^st century BC. The shipwreck was discovered in 1989 and was subsequently surveyed and excavated from 1989 to 1996 by the Archaeological Superintendence of Cagliari and Oristano, in collaboration with the National Institute of Nuclear Physics of the Gran Sasso.

The wreck, which lies on the seabed at a depth of about 100 feet, is located 6 miles from the coast and just over a mile southeast of the island of Mal di Ventre. It owes its extraordinary archaeological importance to its contents, which included a load of lead ingots, the biggest quantity of such ingots documented in the ancient world. It is assumed that the ingots were a part of or the main cargo on the ship.
The only remains of the hull, which was estimated to be approximately 36 by 12 meters, was the central portion of the keel, which extended about 10 meters. This portion of the keel remains because when the ship sunk, the keel went to the bottom of the sea floor where it was protected from the action of the sea. The remainder of the wreck was not protected and was gradually damaged until it disappeared completely.

The load placed in the center of the ship consisted of about one thousand ingots, all trapezoidal in shape, with slightly convex upper surface, and measuring 44-46 cm x 8.5-9 cm x 8.5-10 cm. Each ingot weighed about 33 kg. Many of the ingots were still lined up and stacked in their original positions because apparently, the vessel sank slowly and almost vertically without tipping the load. The ingots each have an epigraphic cartouche (mold marks) bearing the name of the manufacturers. The majority of ingots, over 700, were produced by the family of Gaius and Marcus Pontilienus. On some of the ingots, the Pontilieni inscription was stamped once and on others several times, in an irregular manner. Some of the stamps contain the letters PILIP, which apparently was in remembrance of a servant of the Pontilienis.
In addition to Pontilieni stamp, the wreck has yielded numerous ingots that can be traced to other manufacturers including Quinto Appio, Lucio Carulio Hispalo, Caio Utio, Cneo Atellio, Planio Russino, Lucio Pilon and Marco or Lucio Apinario.

Near the wreck, excavators have also recovered several lead anchors and anchor stock, three grapnels, two sounders, some basalt millstones, a fair number of transport amphorae of the type Dressel 1b (mostly fragmentary), rare ceramic vessels, pieces of bronze vases, a lamp, ceramic lids, an iron dagger, about two hundred lead bullets, and one coin. A very large iron anchor was found in place on the bow. An abundance of lead nails was also discovered and a lead pipe thought to be a part of the bilge pump.

The only parts of the ship that were preserved are in the center of the hull, where they were protected by the load of ingots. This includes the keel, which was attached to the right part of the hull with long nails; the lead that covered the keel; some of the quick work (submerged planking); and many acorn shells, which stuck to the outside of the boat during stops in ports.
In collaboration with the National Institute of Nuclear Physics and the Institute of Isotope Geochronology and Geochemistry, CNR of Pisa, numerous analyses were undertaken on the ingots. The results of these analyses have been published and presented at various exhibitions in Europe and America. The analyses have demonstrated the exceptional purity of the metal in the ingots, which came from the Sierra mining region of Cartagena, Spain, which is also probably where the ship sailed from. The final destination of the ship is not known.