[Ryland]

If you really want to get good mileage and are not towing your boat across the state, I would look at something like the Toyota Corolla station wagon from the late 1980's, they would get 30+mpg and had 4 wheel drive with a 6 speed where they had a sub 1st gear/low speed for crawling along, they would tow 1,000 pounds, haul your kids too.

Other thing to think about is just a 2 wheel drive vehicle with good snow tires, part of snow tire design is wet traction, something you need to pull a boat out and at that point you could get away with pretty much any decent car that had a solid enough body to put a trailer hitch on.
Either way, good snow tires on a 2 wheel drive car can be better then a 4 wheel drive vehicle, besides many 4 wheel drive vehicles are not designed to drive over 55mph in 4 wheel drive.

Or if it's only a few times a year that you use the boat, rent or borrow a vehicle, that is what I've done with my boat.