It's quite apparent that Tom Hanks grew a beard for the movie: One can make out the un-tanned skin at the edge of the beard.

Yet when Chuck Nolan is rescued after being adrift for days unprotected in the sun, it seems that the most important thing he could think of doing was to shave the beard off and to tan out his face...

Note the glaringly obvious evenness of the the tan on his face... I guess, after being sunburnt out at sea, you'd think that the last thing he'd be doing is lying around getting a tan...