Tom,
We've stumbled across significant differences in the past between my '82 and earlier model years, so keeping that in mind......
I assume you are talking about the starboard locker under the sitee in the saloon. Mine contains the fiberglass water tank, tabbed into the hull, but I know the tank was on the port side in earlier models, and my owner's manual even shows it that way. Anyway, since the water tank is there, my starboard locker has holes drilled in the upward curve at the aft end, near the inboard face of the locker, for the water hose running aft from the tank and for hot and cold water hoses running forward to the lavatory sink, effectively draining the locker into the bilge, though I think not at quite the lowest point.
Even if Hunter made no change to the fiberglass liner configuration between model years, not being at the boat, I don't know how much clearance there is for holes on the inboard side, but I know it's tight. Drilling a hole at the aft end of the locker might be a safer bet if there is doubt about the locker being lower than the cabin sole, but you may still need the sponge for the last bit of water.
I'm not sure this helps. Hopefully, someone with a '79 can respond with more confidence.