Which medieval emperor drowned in a river?

The Holy Roman Emperor, Frederick Barbarossa, was a man who’d changed history during his lifetime and changed, it, too, by his unexpected demise. After taking the cross, Frederick had chosen to take the overland route to the Holy Land, and the decision proved to be a fatal one. On June 10th, 1190, he drowned while attempting to ride his horse across the River Saleph in Armenia. His loss doomed the German crusade; only a few thousand of his large army managed to reach the siege of Acre and his eldest son, Frederick, died of a fever soon after his arrival in the Holy Land. Frederick was a legendary leader, bold and charismatic, shrewd, charming, and ruthless when need be, and had earned considerable prestige in his long life; he was 68 at the time of his death. It is possible that he would have been able to keep the rivalry of the much younger monarchs, Richard and Philippe, from degenerating into the hatefest it became, and that would have impacted the crusade. His death and that of his son at Acre also had enormous consequences for Germany, for his next son, Heinrich, was then able to claim the imperial crown, which would have dire results for the Lionheart and for the Sicilians and for many of his Germany subjects. So I would include Frederick Barbarossa’s death in the What If game we like to play here.