Researchers have begun exploring the wreckage of the Mars, a Swedish war ship that sank during a naval battle in 1564."It's a unique ship," . When it exploded, because it actually exploded during the fight, it went down to the bottom ... but we are also diving on the sunken battlefield."The ship sank during a bloody battle against a fleet from Denmark and the German city of Lübeck. Mars was rumored to have been cursed because many of its 130 cannons were made from melted church bells.