How Much of a Cruise Ship Is Underwater?

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Modern cruise ships are massive entertainment and leisure vessels that are places of great fun, enjoyment, and joie de vivre. They provide outlets for cruise ship passengers to enjoy various activities, from dining to drinking to music, kids’ activities, and more.

There are different sections of modern cruise ships that go from the bottom deck up to the top, sometimes 20 stories above the water. In this article, we explore what goes on on the lower decks, get some facts and figures about cruise ship measurements, and understand how much of a typical cruise ship is underwater.

Cruise Ship Weight, Length, and Height Statistics

How much does a cruise ship weigh, how long does it measure, and what is its height? Well, the 50 largest cruise ships in the world weigh over 100,000 gross tons. Royal Caribbean International owns the four largest ships in the world.

In terms of height, the average Royal Caribbean International cruise ship measures 14 decks (stories) high. Length-wise, these RCG ships are 20% longer than the Titanic at an average length of 325 meters (the length of several football fields). 

The Physics of Water Displacement

As it applies to cruise ships, the physics of water displacement is based on Archimedes’ principle, which dictates that the amount of fluid displaced by an object equals its upward buoyant force.

Cruise Ship Under Water
Cruise Ship Under Water (Photo Credit: aquapix / Shutterstock)

To expand on this principle, according to a professor of Naval Architecture and Marine Engineering at the University of Michigan, ships have to displace an equal amount of water to how much they weigh. To do so and to stabilize the ship to prevent a draft, the ship architects designed wide hulls.

That means the vessel has to be extremely wide to compensate for the weight-to-water ratio. Approximately 30 feet (9 meters) of the average large cruise ship sits underwater, but as you’ll see below, there are more understandable ways to measure this.

What’s on the Lowest Deck?

The lowest deck on a ship usually contains the nuts and bolts of the ship. On cruise vessels, it is known as the orlop. Most of the time, the lowest deck has the morgue, fuel tanks, fresh water reserves, laundry room, medical center, jail, and engine rooms. It can also contain crew quarters.

Lower Deck on a Cruise Ship
Photo Credit: Ihor Koptilin / Shutterstock

The lowest deck is typically off-limits to passengers – the fun is all on the upper decks, and passengers tend to board at Decks 4 or 5. Sometimes, however, the lowest deck is available, and passengers can book accommodations to alleviate seasickness.

Layout of a Cruise Ship

It’s essential to understand the overall layout and structure of a cruise ship – not only to familiarize yourself with the various parts so you can navigate it well but, for this article, to understand the ship’s lower decks in context. 

The following are the different locations within your average cruise ship:

  • Aft – Ever heard of the “aft of a ship?” This is the penultimate backmost part of the ship, close to the stern. 
  • Bow – The front of the ship.
  • Bridge – ”All crew to the bridge!” You can almost imagine Captain Picard from Star Trek summoning his crew to the main control section of the ship, usually found at the bow. 
  • Cabin – Sectioned, private living quarters. Akin to a hotel room. 
  • Deck – A given level of a ship. 
  • Galley – The kitchen, where the chefs whip up great cuisine.
  • Hull – The central body of the ship.
  • Lido Deck – Entertainment central! This is where the pool, bars, restaurants, and fitness center are located.
  • Midship – The veritable middle of the ship!
  • Port – The left side of the vessel when facing the bow.
  • Starboard – The right side when facing the bow.
  • Stern – The backmost part of the ship.

Navigating Cruise Ships in Various Types of Water

Knowledge is power, and knowing how captains operate cruise ships in different depths and types of water currents can help you feel safe and secure. 

First of all, cruise ships must dock in water that is at least 25 to 50 feet deep. What factors in here is the draft, which is the measurement of water between the water line and the cruise ship’s bottom hull. 

Thinking about how much of a cruise ship is underwater is best conceptualized as a percentage of the vessel rather than feet. The ship weighs in differently when unloaded and loaded, which affects the displacement. Therefore, the math best works out in ratios and percentages – one part of the ship in relation to another or the water underneath.

Cruise Ship Under Water
Image Credit: Alex Oakenman / Shutterstock

We have already conveniently determined the number of feet an average cruise ship sits below water, but what is the percentage? Approximately 40% of the average cruise ship sits below water. The larger or higher the ship, the less of it is in water. This may seem counterintuitive, but this is how math and physics work out!

This percentage is constant. When cruise ships set sail and navigate deeper and perhaps more rapid waters, still, 40% sits underwater. Now you know the ins and outs of determining a cruise ship’s displacement – and can explain it to your friends!


It’s fun to think about how much a cruise ship sits below water. As we’ve seen from our analysis, several factors go into approximating this figure. They range from how densely packed the ship is when it’s loaded or unloaded, and how large the ship is by height, width, and weight.

Read Also: Underwater Cruise Ship Rooms – What Are They?

We also discussed how much water needs to sit below the ship when it docks and learned about Archimedes’ principle of water displacement. You also found out what goes on in the lowest deck of your typical cruise ship and where most of the action happens. Lastly, we went over the different parts of the ship. 

You’re now a cruise ship anatomist and amply prepared with the knowledge of how they work on the water so that your next vacation is sublime.

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