WM Seaworthy RIB

[Tony B]

I have an older (1994) Seaworthy 9' RIB. I believe it was sold by West Marine back then. It has 2 Drain Plugs. One upper to drain the boat and one lower to drain the Fiberglass rigid bottom itself?

What is this plug for?
Ballast?

[model 10]

The space between the liner and the hull. You could wear a hole in the outer hull or a tape leak along the edge and drain it, where as our rib would sink