I wear a 7mm O'Neil one piece when I play, and a 7mm Kettenhofen 3 piece when I work. I've had the O'Neil on down to 52 degrees at ft+ and while I do feel the thermals, I'm still very comfortable. I may try a dry suit someday, but for now, I'm all wet......you know what I mean.
On the Side, the Conditions are great right now and I'm figuring on a Santa Barbara Island trip the last week of April to photo some Sea-lions. I usually take the "Sand Dollar" out of San Pedro. Always a good time.