Used in larger dinghies and some small yachts. The daggerboard is a centreboard which, instead of pivotting about a pin, is raised or lowered vertically. Used mainly in smaller dinghies. Hook your feet under these when hiking out - if you don't you'll fall out. They also have an annoying habit of breaking, in which case they should be kept locked shut.
Most boats are double-hulled .
A bung is just a hole in the outer hull with a sealing cap, which can be opened to empty out any water which somehow managed to get into the gap between the hulls .