Deepsea5
Former Public Safety Diver
I dive wet all winter here in Nova Scotia. The key is you have to have a method. The ocean may be as high as +15C as late as Dec. (but air temps. near 0C), but as low as near freezing by March, and only maybe +5-7 by May when the weather warms up (16-18). I haven't dived lakes in winter but here they are usually ice covered at some point.
I do one dive in a day, usually about 20 minutes. Have to have a procedure that limits your time exposed to the cold air before (especially) and after the dive. I don my wetsuit at home and drive maybe 1/4 mile to the site, using plastic on the driver's seat for the wet trip back. Everyone's situation is different, so you have to develop your own method that fits. Good luck.
Oh, I never bought a drysuit because for years we did 3 winter months in Florida (in case you're wondering why I'm crazy).
And like JimBlay says in the next post, you may need some sort of warm shelter for before & after the dive(s). It's the air/wind that is the concern. Within a reasonable time limit, you can dive in water that's almost freezing in a wetsuit if you can get warm immediately upon exit (and start off being reasonably warm). I have dived in as cold as 33F ocean water (+less than 1C).
TMHeimer: what you do sounds like what my Public Safety Dive Team did, back when I did that type of diving. We would drive to the dive scene with our personal vehicles (or patrol car, if on duty at the time). If we responded with our personal vehicles, there's a good chance we had time to don our wetsuits before responding. Most of the time we would drive home or back to the Sheriffs Dept to change back into our civvies or uniform.
One thing we had in our favor was an ambulance that we converted into our Dive Team vehicle. We used that vehicle as an equipment transport/storage vehicle, a place to warm up and a place to change clothes/don wetsuit if need be. We could also heat water for coffee; and more importantly, to warm up water that we would place in Thermos bottles. With our wetsuits already donned, we would dump the Thermos full of warm water in our wetsuits just prior to entering the water. That was a BIG help in adjusting to the water temp.
FYI: The only regulator set I own is a Scubapro MK-2 first stage/Scubapro G-250 second stage. That is the setup I've been using for 30 plus years, even for ice diving. I used to run a Scubapro AIR2, but have since swapped to a Scubapro R380 octo.
Some people say you will DIE if you ice dive with my setup! LOL I never had a freeze up. As I'm sure you well know, ice/cold water diving requires extra prep/caution.