Axel Oxenstjärna was the Lord High Chancellor of Sweden during king Gustavus Adolphus II, who fought in the 30-year war. Not exactly medieval, but fits the description otherwise.
While Gustavus was a brave soldier, he was known to be a bit foolhardy. Besided getting himself killed in the battle of Lützen 1632, the story of the Vasa ship may have been what Oxenstjärna had in mind. Against the advice of his engineers, the king ordered his new flagship to be loaded with so many guns that she capsized and sunk outside of the Stockholm harbour on her maiden voyage only having sailed a short while.
Yes, definitely worth checking out. The ship was preserved very well in the oxygen-depleted waters of the Baltic and is almost in a pristine condition.
This is very off-topic, but I cannot resist mentioning that when the ship was recovered from the bottom of the sea in 1961, one of the first things discovered from it was a miniature statue of Finnish olympic winner Paavo Nurmi. One of the best pranks by the student association of the Helsinki University of Technology. https://www.reddit.com/r/todayilearned/comments/62jm2z/til_i...