Pirates: Duels on the High Seas

An old man in a pub presents you with a riddle; after solving this riddle, you discover that possession of seven magical keys will provide you control over the seas. After collecting the first Key from Port Royal, you find a scrap of paper which informs you that unless you obtain the other six keys in six days' time, you will perish.
The keys are spread throughout the Arctic, Bermuda Triangle, China Sea, Java Sea, Persia, Port Royal and Porto Bello levels.

Source: Wikipedia, "Pirates: Duels on the High Seas", available under the CC-BY-SA License.