A cat or a dog (no reference to size or weight that I could find) that the sand/surf action has abraded the hair off of.
Alternately, it could have been a similar sized forest creature which had the hair singed off in a forest or grass fire and fled to the water and subsequently drowned, I’ve seen skeletal remains of quite a few of those.
Cyrano told me today Jeff Corwin said it is probably a raccoon.
THe hair will begin to fall out not too long after death especially when kept wet. When you skin an animal for its fur you must treat the pelt ASAP so that the hair does not ‘drop.’ There was a girl from my hometown who disappeared for a couple weeks after I married and moved away. They found her in her car in the river. All her hair was already gone. I can’t remember how long it was that she was missing though.
http://www.essortment.com/all/smallhideshow_rioi.htm
“ When tanning pelts, you must be careful to not let the pelt stay wet for too long or the fur will fall off. “