Because whenever he captures an enemy ship, Gangplank likes to take the captives and gang up as many of them on the plank at once, just to see how long they can last before they meet their watery grave.

So far the record's been 8 men for 10 seconds.

The plank you speak of is referred to as a "gangplank," just in case you were wondering...

Pffft, when has anyone ever refered to the plank as a gangplank? Never heard no pirate say "Make 'em walk the gang-plank!", no siree bob.

That's still what it's called though.

The gangplank is actually the board that you walk across when going onto a ship from the dock

In reference to the champion not the object.

I thought it was due to reasons of another kind >_>