– Seven years after it was found, a 454-year-old shipwreck in the Baltic Sea is still revealing its treasures. Cannons, a hand grenade, possible remains of helmets and swords, and a large grappling hook used to rein in enemy ships are among recent discoveries aboard Mars, a Swedish warship that sank following a battle in 1564 with Danish and German soldiers, reports National Geographic. The battle was "an absolute ruckus," as archaeologist Rolf Fabricius Warming puts it to ScienceNordic, describing grenades, lances, and spears hurled from the tops of enemy ships at Mars. The vessel had an anti-boarding net, but as many as 400 enemy soldiers were among the 800 to 1,000 on board when a gunpowder explosion at Mars' bow sent it to rest 250 feet below the sea's surface near Öland. "It was so violent that the front of the ship lies [130 feet] away from the other remains," says Warming, noting any soldiers not killed in the explosion would have drowned. In the latest search of the untouched wreck by divers and underwater vehicles, "we have come closer to the people aboard," he adds. "We found more skeletal parts, including a femur with trauma around the knee which we believe to stem from a sharp-edged weapon." But it's the grappling hook Warming finds most exciting. He calls it "totally unique," noting no other examples from the 16th century exist, except in illustrations. The hook will remain where it lies, however, along with silver treasure previously found. Researchers haven't been granted permission to disturb the wreck, which lies in cold, low-oxygen water ideal for preserving wood. (Legend has it the ship was cursed.)