Researchers exploring the depths of volcanic Lake Nemi in Italy are hoping its waters have one more secret to give up.

A diving team in partnership with officials from Italy’s civil protection agency are hunting for the remains of one of Roman Emperor Caligula's massive floating palaces. The infamous ruler, who briefly presided over ancient Rome some 2,000 years ago, is said to have used the barges to host wild orgies, cruel games, and other depravities associated with his reign. As such, the ships were outfitted with elaborate comforts ranging from marble floors to extensive gardens and even temples.

"He built Liburnian galleys with ten banks of oars, with sterns set with gems, particolored sails, huge spacious baths, colonnades, and banquet-halls, and even a great variety of vines and fruit trees; that on board of them he might recline at table from an early hour, and coast along the shores of Campania amid songs and choruses," wrote Caligula's biographer Suetonius. "He built villas and country houses with utter disregard of expense, caring for nothing so much as to do what men said was impossible."

After Caligula's assassination after only three years on the throne, his party boats were scuttled and sent to the bottom of Lake Nemi. For centuries, fishermen reported snagged nets and hooks that would occasionally bring up pieces of the boats.

It wasn't until the early 1930s, under the orders of Italian dictator Benito Mussolini, that Caligula's party boats once again saw daylight. Using an old Roman drainage tunnel that at one time provided irrigation to farms below Nemi, engineers lowered the lake's level by 66 feet.

Two vessels, measuring 230 feet and 240 feet in length respectively, emerged from the mud. You can see footage of the reclamation efforts and remarkable state of preservation of the 1,900-year-old remains below.

The ships and their artifacts astonished both archeologists and naval experts alike, shedding new light on the advanced construction techniques of the Romans in the first century AD. Besides an anchor design that was originally thought to have only been invented in the mid-19th century, the researchers also found an elaborate pump system.

"Both of Caligula’s Nemi ships contained several hand operated bilge pumps working like modern bucket dredges, the oldest example of this type of pump ever found," writes Kathy Warnes. "Piston pumps on the two Nemi ships supplied hot and cold running water through lead pipes. The Romans used the hot water for baths and the cold water for fountains and drinking water. This piston pump technology later was lost to history and not rediscovered until the Middle Ages."

While the Italians successfully recovered both vessels from the bottom of Nemi, their subsequent study and display was short-lived. On May 31, 1944, Allied bombs struck a German anti-aircraft battery near the Lake Nemi Museum. The explosion generated a fire that destroyed the remains of both ancient ships.

A third and larger vessel?

Despite the loss of two of Caligula's barges, rumors persisted that a third, larger vessel remained safely hidden under Lake Nemi. In the 16th century, a diver named Francesco de Marchi used an early version of a diving bell to descend to a deeper area of the lake not drained by Mussolini's engineers.

“He reported bringing up relics on the far side of the lake from where the two other boats were found, and talked of a boat measuring up to 400 ft long,” Alberto Bertucci, the mayor of the town of Nemi, told History.com. “Since then we have oral testimony from fishermen bringing up items in the nets at that spot."

The divers engaged in the study are using sonar and ground-penetrating technology to pierce's Nemi's muddy depths.

“If it’s down there, and it’s that long, then we are talking about the world’s first luxury cruise ship,” Bertucci added to the Times of London.

According to Carlo Cestra, whose company specializes in accurate 3D reconstruction and animation of archeological sites, the divers will search Lake Nemi through April 12th.

You can see some digital recreations of the previous two Nemi vessels recovered in the 1930s below.

A digital recreation of how the first wreck was revealed as water was pumped from Lake Nemi. A digital recreation of how the first wreck was revealed as water was pumped from Lake Nemi. (Photo: Used with permission from Carlo Cestra/Carlo Cestra Digital Productions)

A digital reconstruction of what Roman Emperor Caligula's first vessel would have looked like in AD 41. A digital reconstruction of what Roman Emperor Caligula's first vessel would have looked like in AD 41. (Photo: Used with permission from Carlo Cestra/Carlo Cestra Digital Productions)

A digital reconstruction of what Roman Emperor Caligula's second vessel would have looked like around 41 AD. A digital reconstruction of what Roman Emperor Caligula's second vessel would have looked like around 41 AD. (Photo: Used with permission from Carlo Cestra/Carlo Cestra Digital Productions)

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.