Getting pics of a sloth in a tree, laying around, etc. is not tough. If you've never seen one, Google makes it easy...these guys just don't move quickly anywhere.
This sight, the furry lump in the water, is rare, according to our guide. He said he's been doing guide work for 20 years and hadn't seen a sloth swimming. These are the three-toed variety, BTW. The two-toed can be found in CR, but they are nocturnal.
