You could tape a bunch of wax paper over the hole and a flat piece across the bottom, then make a plug from expanding foam.
We have artesian wells down here, and a few years ago a guy on a tractor hit one, breaking off the 6" pipe just above the ground. The well free-flows 60 gpm with a fair amount of pressure. To stop the flow and get on a new valve, they stuck a big balloon down the flowing well and inflated it. Maybe a smaller plug with an inflatable collar?
I have been tropical storm sailing lately, and take enough water aboard that I want a way for it to drain out. That could get less fun when the water gets cold, but that's months away down here. I'm going to ask Santa for a wetsuit.