How does Beowulf answer Unferths allegations? (section 8)

While Beowulf is proving himself to the company of the Danes, Unferth, the maker of discord enters the scene. Unferth's job is to test the actual valor of the warrior and his ability to fend off a verbal attack. Beowulf not only answers the challenge (yes, he did win the contest), he also shows the extent of his bravery (he defeated the sea monsters) and discredits Unferth's truthtelling (Unferth is nothing but a drunk murderer who can't act).