(Home, DVD, etc.)
Prince Valiant started life as a serial comic in 1937. By the time this film was greenlit (1952 or 53, I presume), the comic’s storyline was so complicated that the screenwriter wound up simply choosing bits and pieces at random and producing a script from them.
It’s possible that that shows.
(Spoilers!) As the film opens we learn that the Christian king and queen of Scandia have been exiled to England and given a nice castle to live in by King Arthur. There they live with their unfortunately-behaired son, Valiant, played by a young and terrible Robert Wagner. (You probably know him as Number 2 in the Austin Power films.) We’re introduced to Valiant in a scene clearly meant to showcase his athleticism and bravery, when he, like, rappels down the castle wall then strips off and plunges into the sea to swim over to some friends (Christian Vikings) who’ve come a-calling in their little Christian Viking boat. (The clever viewer will infer that they’re Vikings by their horned helms, shaggy beards, and animal-skin loincloths. Also because the word ‘Viking’ is used about 3 million times in this film.)
Tangentially, Robert Wagner has a nice abdomen. I googled 'Robert Wagner shirtless' to prove it to you, but couldn't find a still of the scene in question. Sorry!