Quick Story:
A Hunter on this website here recently was in a situation he was hunting the Wabash river and was swamped but he was rescued...Again he had a boat like the MOMARSH boats which was adequate for the situation he was hunting...And he was by himself...He probably had years of waterfowl experience under his belt...But the fact is the situation happened on smaller body of water unlike Lake Michigan...If he would have been in that situation he probably would tell you himself he would not have made it....
I am currently building a broadbill and I am sure a lot of members on this sight would agree that it is a fairly stable boat in big waters...But I would not recommend with decoys, yourself, and a gun hunting in big, frigid waters by yourself. The prime factor is to have a boat which is stable to the water condition you are hunting. In large waters you will need to have a deck on it with a small or minimal opening...100 yards or so off shore is a long swim no matter what condition you are in and two the waters of Lake Michigan is hypothermia's dream situation....
I kayaked this summer from the Michigan shore to South Manitou Island, roughly 8 miles offshore...The kayak I own and built is a Pgymy Coho...It is very stable and can handle extreme conditions. The lake that day was still with calm, rolling waves of 3 to 4 foot with the water temperture about 56 degrees 100 yards off shore...I did roll a few times just to cool off from the 75 degree sun beating down on me...But you can not imagine the few short seconds under water how frigid that condition was, I didn't see my manhood for hours later...I could not image that same situation when the air temperature is 40 degrees or below with wind...Granted this boat is narrow and is able to roll by design...
We all do some crazy things when it comes to our passions...I know I have...I would hate to see another duck hunter end belly up due to being in a situation that they didn't have at least the minimum proper requirements of a boat in that situation...Even when properly fitted some times it is just not worth it...
The prime idea would be to hunt with a boat which in this case you were swamped could get you back to shore...If your diver hunting they will come in to most decoy setups as long as you are still and resemble something that would be as a natural setting in the water, such as a rock. No matter how calm the water is...There are exceptions to some birds but I still think you should invest some time and or money in a decked boat where at least the width of the boat is a 3rd as wide or more the total length of the boat for stability....And two since you are hunting alone you might think about purchasing a dry suit just in case shit does happen, there expensive but $600 is worth a lifetime...The choice I would recommend to purchase and not build would be a Barnegat Bay Style Sneakbox with a displacement instead of planing hull...There are a handful of people on this sight whom build them in the price ranges of $1200 to $3000 and you would be getting a satifying product for years to come...Of course if you are like me short of funds you might want to invest in the Broadbill or simliar boat to build yourself...It isn't rocket science to build but it will take 60 or so hours of your time over3 to 4 month period...I have estimated cost of around $1200 to build this boat to what I am wanting with the grade of wood and accessories on the boat. I have viewed guys build the same boat for $600 with change...Ask Eric Patterson on this website about this...He will have a lot of insight as well as others....
Good luck with your choices...