I don't remember a hose like that on our C-18, or at least coming out of the liner like that. We had a manual bilge pump in the locker, with a removeable handle that come into the cockpit. The discharge for the pump was out through the transom. Try looking in the keel sump for the other end.
The inner space between the liner and the hull is filled with expanding close cell foam at the factory. You'll see plywood covers in several locations under the cushions, and in the cockpit locker. The close cell foam will not absorb water. Very similar construction of how Boston Whalers are made. This is why the C-18 is un-sinkable. It also is VERY sticky stuff and after it cures, it further bonds the hull and the liner together making the C-18 an extremely rigid and strong boat. She'll take more that you can.
GREAT little boats!
Don
