What Is The Bottom Of A Ship Called?

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Have you ever found yourself staring out at a cruise ship wondering what all the different parts are called? Well, wonder no more! In this post, I’ll talk about the one part of the ship that you can’t actually see: the bottom. 

What exactly is the bottom of a ship called and why is it red? Keep reading to find out!

bottom of a cruise ship

What is the bottom part of a ship called?

The bottom part of the ship is often referred to as the hull, but the hull of the ship also includes the sides below the gunwale. The lowest part of the ship is the keel, which is the centerline structure that forms the foundation of the hull.

The hull is the water-tight lower part of the ship which includes the bottom, but also the sides of the ship. It extends down under the water but also upwards to the lower decks of the ship. 

Recently, I visited the SS Great Britain, the world’s first great ocean liner. We were able to walk underneath this incredible ship and see the shape of the hull.

The hull of S.S. Great Britain
The hull of S.S. Great Britain

Hull Vs Keel

Modern cruise ships have U-shaped displacement hulls which are designed to displace water and this is what makes a cruise ship float.

The keel is the backbone-like structure that holds the hull together and gives it its shape. It’s definitely at the bottom of a ship but is not often used to describe the bottom of the ship.

Both of these terms can be used to describe the bottom of a ship although they both have a more specific meaning than that. 

Spectrum of the Seas under construction
Spectrum of the Seas under construction

There are a couple of other words that can be used to refer to the bottom of a ship, one of them is kind of obvious and not hugely scientific – the bottom. 

Yep, it’s that simple! Mariners will often refer to the part of the hull below the waterline as the bottom of the vessel. It’s much easier to learn than most parts of a ship! 

Another term that you could use to describe the bottom of a ship is the underside. Again this is a fairly simple and self-explanatory term.

So, while the term hull is probably the most commonly used term to describe the bottom of a boat, it’s not the only term that you can use and it technically describes more of the ship than just the bottom. 

If in doubt, you can always just refer to it as the bottom of the ship, safe in the knowledge that this is an accepted term amongst mariners. 

What is the bottom deck of a ship called?

The bottom deck of a ship is called the orlop. This is the lowest deck on a ship and is typically situated below the water line. The orlop is often used for storing cables. It’s possible that the term orlop has come from the practice of over-looping cables.

ship orlop deck

But this is not known for certain, another theory suggests that it could be a variation of “overlap,” which refers to a partially overlapping balcony half deck that could be found in parts of the lowest deck’s area.

Suggested read: What Is Deck 1 On A Cruise Ship?

What is in the bottom of a cruise ship?

In the bottom of a cruise ship, you’ll often find the engine room, clean and dirty water treatment systems, air conditioning, fuel bunkers, water storage tanks, and extensive plumbing. It’s quite likely that you’ll also find quite a lot of the crew cabins in the bottom of the ship. 

ship engine room

Basically, in the bottom of a cruise ship, you will find all the noisy, smelly, dirty things that you want to keep away from paying passengers. And of course, the quarters of the lovely staff who definitely don’t smell!

The cruise ship engines are usually found towards the aft of the ship and will be located in the position that they are most effective with the other spaces designed around them. It’s very rare to find underwater cruise ship staterooms

How far underwater is the bottom of a cruise ship?

The bottom of a cruise ship is usually between 5 metres (16ft 5in ) and 10 metres (32ft 10in) underwater.  A typical cruise ship extends around 8.5 metres (25ft 6in) underwater. This is tiny in comparison with the huge overall height of cruise ships. 

The depth that a ship extends underwater is known as the draft. The depth of a cruise ship draft will affect which ports it’s able to dock at and a deep draft could limit opportunities to visit interesting places. This is why cruise ships are designed to have a far shallower draft than comparably sized container ships which only ever head to deep water docks.

bow of a cruise ship

What does the bottom of a cruise ship look like under the water?

The bottom of a large ocean-going cruise ship will usually have a U-shaped displacement hull under the water. It looks flat from a distance but on closer inspection, you will see contour bends at the edges and at the bow and stern of the ship. 

Suggested read: Bow Vs Stern

The bottom of a cruise ship is wide and flat, this helps to keep the ship stable even in choppy seas. 

At the front of the ship you will often find a bulbous bow.  This is a large rounded projection that sticks out in front of the main hull of the ship. The aim of the bulbous bow is to reduce the ship’s fuel consumption by changing the way the waves move along the hull.

the bottom of Symphony of the Seas cruise ship

At the back of the ship (stern), you will find the ship’s propellers or thrusters. The main hull is often raised in this area with the propellers projecting downwards. 

The propellers can be huge at around 6 metres (20 feet) wide. Some ships also have smaller side thrusters near the bow. These are used to help guide the ship into position when the ship docks at a port.  

Ship propeller

You can see the keel running through the centre of the hull and cruise ship bottoms also have bilge keels and fin stabilizers to help them stay upright. The angle of the fin stabilizers is adjustable and can be changed to mitigate the force of waves against the ship.  

When you look at the bottom of a cruise ship under the water you might also see some more natural features since sea life like algae, plankton, sea grass, mussels, and barnacles can attach themselves to the hull.

Why is the bottom of a ship painted red?

The bottom of a ship is often painted red as it’s a nautical tradition to paint the hull of a ship in red. This tradition has developed from a time when ships were made of wood and reddish copper paint was used to preserve and protect the wood. 

SS Great Britain hull painted red
S.S. Great Britain’s hull painted red

Copper coating was used as a biocide to protect the hull from anything that might degrade the ship over time. The copper paint would protect against worms eating the wood, and barnacles, seaweeds and algae attaching themselves to the ship when in the water. 

These types of creatures can cause damage over time and they also add to the weight and drag of a ship making it less efficient.

These days, antifouling paint can be made in any colour that you like, but seafarers are a traditional bunch and more often than not ships are still painted red on the bottom. Sometimes, they’re painted blue.

Man from Royal Caribbean looking at the ship

There is a second reason why it’s a good idea to paint the bottom of a ship red.  The red paint contrasts well against the colour of the sea, making it easy to see. This makes it easier to tell if a ship is overloaded and sitting low in the water, and makes the ship easier to spot from above in case of an emergency. 

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Cruise Mummy

Jenni Fielding is the founder of Cruise Mummy. She has worked in the cruise industry since 2015 and has taken over 30 cruises. Now, she helps over 1 million people per month to plan their perfect cruise holidays.

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