bungs are on the outside of the boat but with a piece of nylon string through so that if out then they don't sink to the bottom.
Go a a chandlery and you can buy rubber bungs the shape of an ice-cream cone. Rubber bungs eventually become hard etc. You could shape cork bungs by getting them from a home brew shop.
Did this on my wooden Enterprise dinghy as part of referbishment.
Malcolm M
March 2014