i'm not formiliar with the wheather in chigaco, but when it get colder you really want a drysuit and a liferaft.

A wet or a drysuit will keep you warm in the water, but only for a limited time. Because your IN the water and exposed to the wind. You also have to time your breathing, because you don't float well enough in a suit.
A liferaft will keep you out of the water, provide protection against the wind and have more survival equipment on board.

I did a maritime survival course not to long ago and i really like a liferaft. You simply can't get the same protection in a suit.

And don't forget a PFD, incase you only got the suit. It keeps you head just a little higher and that makes a big diffrence. Atleast when it's properly fitted.