Lake upto 41 degrees!

Yes, the earplugs make all the difference in the world, BUT that's just to stop the horrible discomfort of cold water in your ears, not to really keep your core warm. Also, keeping the cold water out can prevent "surfer's ear" which is the buildup of cartilage in the ears due to cold water exposure. I wear two rubber caps on my head and feel fine (my face is cold though, but it's almost pleasant after a while). I got an XTerra wetsuit for an amazing sale price last year and only had my first real swim yesterday (1/2 an hour in 45 degree water) - the shock was bad getting in but after a few minutes swimming it was as if I wasn't even wet. I was quite comfortable. The suit is called Vortex, and says it has 5 mm thickness in the body and variable amounts elsewhere. Depending on how much you can stand the cold, though, I think most suits will help keep you warm enough to swim in mid-40s water. Hope this helps.

Yes, the earplugs make all the difference in the world, BUT that's just to stop the horrible discomfort of cold water in your ears, not to really keep your core warm. Also, keeping the cold water out can prevent "surfer's ear" which is the buildup of cartilage in the ears due to cold water exposure. I wear two rubber caps on my head and feel fine (my face is cold though, but it's almost pleasant after a while). I got an XTerra wetsuit for an amazing sale price last year and only had my first real swim yesterday (1/2 an hour in 45 degree water) - the shock was bad getting in but after a few minutes swimming it was as if I wasn't even wet. I was quite comfortable. The suit is called Vortex, and says it has 5 mm thickness in the body and variable amounts elsewhere. Depending on how much you can stand the cold, though, I think most suits will help keep you warm enough to swim in mid-40s water. Hope this helps.