i've been out surfing in sub-zero.
dry suit, 2 pairs of gloves, hood, thick boots.
nice feeling to see snow lying around at the beach
but if you do something like that, there are different rules:
don't go out if the wind is the slightest bit offshore (i lost a kite and nearly died because of that), only go out in shallow waters - without a big directional, i guess you will swim, even with a drysuit, for about 10-15minutes till you stop moving. and you're slower than usual.
ideal would be:
shallow water, side-onshore, sunny weaher and someone who's watching you!