Personally, I wouldn't be very inclined to try to swim the canal. Basically, not only are you going to increase your risk by becoming cold and wet, potentially soaking your gear, but you could get run over by a boat.

My approach is to know about all the alternative crossing points (make sure you have maps), and chances are at least a couple of them will be passable.

Even if that doesn't work, remember that after Sept., 11, boats voluntarily started ferrying people away from the area. While you can't rely on it, I suspect there is a reasonable chance something similar will happen. There are just too many boats and too many people wanting to get across. Potential will happen.

If all else fails, you could 1) Wait. Something is going to happen, or 2) Go the long way around (south around the lake). Not optimal, but I suspect one of the other things will pan out before that is required.

If you are warm dry and healthy, you are not in immediate danger. Don't put yourself at increased risk to cut a bit of time. Well... Unless you are Bear Grylls. In which case... Have fun!

-john