The fabled bear from the cave ran off while I was fighting, exiting the cave. I followed and killed it on the beach, but before I could skin the bear, its body rolled into the ocean. It is just out of reach. We should be able to use tools while in the water, even it means we sink to the bottom. (we should be able to swim back up)
You should be able to use throwing knives to skin creatures from a distance, then do a fly/swim over and hold E to collect all the mats.