I know it is hard to believe, seeing how a snapping turtle behaves out of it's element, but when in water, snapping turtles are not aggressive. The defense mechanism is only active on land. I have put large snapping turtles destined for the table in water filled tubs to let them purge for a few days, and once in the water they are a totally different animal. You can literally step on one in the water, and expect no recourse. Test it out yourself. It will put you mind at ease. If you remove them from your pond, more will move in.
