This might work. I'm really concerned about water having the ability to get around the sabots, which seal the powder on each side. I know Knight did a demonstration awhile back where the put one of their loaded Disc rifles in a water tank for an extended period - and it still fired. Seems as though those sabots seal out water pretty well.

I'll try the bullet puller from the breech end - and attempt to pull the bottom bullet out sabot first.