There are two groups of ice boat sailors, those who have been swimming and those who are going to go swimming. Wearing a dry suit makes the thin ice swim a non event, you may get wet feet or hands. YOU STAY WARM and have plenty of non panic time to get out of the water and retrieve your boat. I have been there, they really work.
This is the time to buy the dry suit. They are worn by kayakers who don’t buy them during the winter. The sporting goods stores don’t want to keep them in inventory until Spring when the latest styles come out anyway. Discounts of 30% or more are common. Hypothermia or worse can be avoided for less then the cost of a used sail or runners. Be sure to get one of breathable fabric. They are excellent wind breakers as well.
THINK ICE, stay warm and dry.