did unferth believed that Beowulf could defeat Grendel ? why or why not?

Unferth is jealous of Beowulf. He tries to cast doubt on Beowulf's courage and strength. During the feast, Hrothgar's thane Unferth tries to discredit Beowulf. He accuses Beowulf of losing a swimming contest with Breca. Beowulf disagrees‹he not only defeated Breca, he also fought off heaps of sea-monsters, thanks to both God and Wyrd. What heroic deeds have Breca, or even Unferth, done? Unferth even killed his brothers, and he hasn't done anything to stop Grendel. Upon hearing Unferth shamed by Beowulf, the whole company laughs.