I recently inherited a 14 foot aluminum riveted boat from a family
friend.
This boat is in decent shape and I was advised there are no current
leaks with this boat.
I am planning to fix this boat up a bit by putting in floor
boards/carpeting and a few swivel seats.

My question is, is there something I can spray or apply to the bottom
of the boat (inside) that will make it waterproof?
I watched a show on the channel World Fishing Network where a couple of
hosts sprayed something and made the boat waterproof. I just cant
remember what it is.

I am trying to avoid having to use putty or something to make bandage
solutions to any leaks.

This is my first boat so any help is much much appreciated.

Thanks,
Gary