Just read the “Is the Camel the only animal that can’t swim?” column, and it’s suggested towards the end that sloths can’t swim.
Saw on cable a few years ago that they can, and this clip says they can actually swim faster than they can move on land:
I raced here to make the same point, but LAV25 beat me to it. That said, I have another interesting tidbit: a long time ago, there were sloths that lived primarily or exclusively in the water: Thalassocnus - Wikipedia
They’re generally referred to as “marine sloths,” a phrase which makes me envision a bunch of sloths with high-and-tight haircuts shouting, “oorah!” or maybe flying Harrier VTOL fighters.