Ha, I can guarantee you that after a New Years Eve dive in the river with a wet suit there was nothing "big" left anywhere. Think
(George Castanza pool scene)
It was back in the late 80's early 90's.
A couple guys we dove with had dry suits and wore the snowmobile suits under neath like mentioned, I never did, they were spendy at the time. We always had a boat following above us that could grab the dive flag and give a tug to let us know we needed to get to surface. The guy with the flag ALWAYS was in the lead. At the night dives we dove with those glow sticks that the people in the boat could see even if your light went out. The process was like what Ahab mentioned. Ride the boat up to the dam and take out at the landing. Some years open water went further south and gave you a longer dive but the ride back to the landing resulted in a frozen wet suit that you could hardly get out of.
Did have a propane heater in the dive trailer though so a few minutes thawing and having a shot of home made schnapps and you were good to go.
We used to do a lot of diving with a good friend that owned the dive shop in Minot (Dakota Divers). Dives in front of the dam could get you down pretty deep close to 100 feet and pretty dark. Had a couple people freak out on those.
There used to be a large tree between Wolf Point and the Dam we called the Christmas tree. Some July 4ths we would have our "Christmas in July" and go get lures off it. Lots of stuff hanging off it including a couple down riggers but you could get wrapped up in fishing line if you were not careful when collecting lures. Had to cut a guy lose once, he never dove there again with us.
I never did like ice dives though, kinda cool walking upside down under the ice, but just not for me.
Diving safe is all in the prep. My friend was one of the best instructors around.
Anyways, there were a few cool deals like this antler found in the river below the dam.