Hole in my boat..

[happychappy]

I had a question about my boat. Its a 1973 16 foot tri it looks like a Glassmaster playmate. I had a question about the area where the plug is. There's a small recess where the plug is. On the wall opposite the plug hole in the recess there's another hole that goes to a chamber somewhere under the floor I put my finger in it and found some water but this was after I had just taken it out of the lake so it could have come from that since the drain cecess was full. My question is whats in there and should that hole get a plug too? Theres no door on the floor and all the wires run along the side to the power and the O/B.

Thanks
Arnold