Unless there is a reason for getting across that is worth your life, find another site or wait.

There are techniques for swimming rapids, but they are for survival situations when you can't avoid going into the water. Basically swim diagonally across the stream with the current. If you are not alone, the 550 cord might help; they can hold it while you swim and pull you back if you don't make it, then you pull them across. Again, in life or death situations.