You’ve seen them on almost every cruise ship, but you may not know what they’re called. To give you a hint: Carnival’s is shaped like a whale’s tail.

Yes, that cute, red whale’s tail on the very top of all Carnival cruise ships is a technically called a funnel. Other terms for this feature on a ship are smokestack, chimney, or stacks.

In times past, a ship’s funnel was originally used to direct smoke and fumes up and out from the coal-powered engines below decks. This not only helped the crew to see what they were doing (not to mention clearing out the blinding smoke was beneficial to their health), it also kept the decks free from smoke.

Once ships began to be powered by steam, funnels were still necessary to help with exhaust gases. Though fewer funnels were required, many ship companies began to realize the value of them as a distinguishing feature of their fleets, due to the design that created a ship’s outline. Ship lines even began to paint their funnels in colors that became a trademark, identifying feature. For example, Cunard’s funnels are painted black and red.

It was once believed that the more funnels a ship had, the more powerful and reliable it was. That wasn’t true; however, ships were built with extra non-working funnels to give that impression. Plus, during the first and second World Wars, by changing a ship’s funnel height or diameter, it helped disguise the ship’s outline.

Today, even though ships’ engines are cleaner running, funnels are still needed to some degree. Additionally, most commercial cruise lines now have their own identifying funnel shapes, with the cruise line’s colors or logos painted on them.

Some ships even have extra funnels for design aesthetics, and Disney Cruise Line has a special use for its forward funnel: it houses the Vibe teen lounge on the Disney Magic and Disney Wonder ships.