Not having the pleasure of
Going In on a Sled I cant' comment except to speculate that your Sled is going to the bottom.
With an Iceboat you will "Land The Boat" ...like landing an airplane..in the water. The Iceboat will fall over on it's side and remain afloat..It's WOOD. The mast will likely tip over and land on "good" ice at the side of the hole you just made. Iceboaters wear the same "suits' as Snow Machine drivers do.
The shock of the cold water will be brief. Then the swimming Ice Boater can "Walk Over" the SAIL to good ice and recover. In my swimming experience, I got out of the water on my own, friends arrived shortly, and then we had to figure out HOW to get the Iceboat out of the water. SO: I WENT BACK in the water to disconnect the wire rigging from the mast to make recovery much easier. An hour later I was sailing again..albeit in a dry snowmobile suit loaned by a friend.
NB