This is NOT a trick question, the gray sheep, for example, hasn't moved in weeks (that's REAL LIFE weeks)! The black one was running around like crazy for days, but when it got there it stopped moving.
Betting you they just don't want to jump in when wearing their wooly coats; all that fuzz just soaks up the water and makes it deuced hard to swim like all sheep can. (Gracefully.)
No, that's a sheep that's been hanging around my island. I just thought I'd give it superpowers (Advanced Genetics)
The gray one is COMPLETELY vanilla, untouched.