[BigLew]

If you want to leave SOME water, as you said, you could mount the water drain inlet/outlet so that it is up off the bottom of the B/W and will only drain/pumpout down to a desired point. This will leave a desired amount of water in the baitwell. You can set it up so that you can move that outlet down to the floor of the baitwell for when you want to "pump" it dry.