You need to tell us which Frederick you have in mind ...
Frederick I Barbarossa von Hohenstaufen b.1122 d. 10 June 1190 Duke of Swabia (as Frederick III) 1147-52 King of Germany 1152-1190 King of Italy (King of the Lombards) 1154-1190 Holy Roman...
Frederick II is the Holy Roman Emperor (1194-1250), the king & emperor
On his way to the holy land during the second crusade he fell off his horse while crossing a river and drowned.