Are you wondering how cruise ships work? Whether you’re planning a trip or just curious about a cruise ship’s technicality or even the logistics, it’s always intriguing to find out how massive ships like work. How does a cruise ship work?

First and foremost, a cruise ship’s heart is in the engine of the vessel. The engine’s design, paired with proper fueling, provides the power for the ship’s mobility and all the entertainment aboard. The ship’s engineering and the logistics of running a cruise company play a role in shaping how a cruise ship works overall

If you are an engineer curious about a ship’s mechanics, this is an article for you. Fortunately, if you’re just a curious traveler wondering how a cruise vessel will shape your next trip, this is also for you, so read on. There is so much to a cruise ship other than the cocktails and fun parks on top. This will be an eye-opening article for all audiences.

How Do Cruise Ships Work

To the ultimate question, “how a cruise ship works,” let’s dive into how it works mechanically. What are the technical and mechanical aspects of a cruise ship? What does an engine do? How does a massive ship provide light, food, entertainment in the middle of an ocean? Is the water safe to drink?

Then, after reviewing how the cruise ship’s mechanics work, the answer to how a cruise ship works logistically can be answered. How do companies make a profit from these vast ships? How do the ships prepare for new passengers?

Technical Aspects of Cruise Ships

The technical aspects are a vital part of a cruise ship, so it will be first visited. Not to state the obvious, but the ship’s heart is shaped by the crew and the engineers that have put many hours and dedication into making a cruise ship work.

This is article will reveal the true hidden layers of what makes it all work starting from ground zero, the heart.

Technical Aspects

If you want one thing in a cruise ship aside from the cocktails and a nice tan, it’s the vessel’s stability and durability. Whether you are traveling through an unexpected storm or cruising on a gentle wave, your cruise ship should be the most stable in all situations.

How are cruise ships stabilized? The general idea for balancing and maintaining buoyancy is distributing the weight throughout the ship correctly, and of course, displacing the right about of water as it moves. So, let’s first talk about one of the most massive machinery onboard, the engine. Where does it sit and how does it run the cruise ship?

Engine Rooms

Where are the engines located? You guessed it, most heavyweights, such as engines, are found as low as possible in the lower decks, ground zero. For most cruise ships, the engines are close to the keel. The structural keel is the most closes to the bottom of the vessel and the ship’s wide hull. It runs the length of the vessel down its centerline and in most ships, you won’t have to go far to find the engine rooms.

Just because it’s placed low in the ship doesn’t mean it doesn’t take a lot of space. For all the ship’s power, the engine rooms can take up several decks high and are generally divided into several compartments. It may not feel like an open massive space, but it is truly the heart of the ship and the design of the rooms and placement are critical.

Usually, the primary concern for most ships is have engines and machinery compartmentalized for safety and avoiding fire hazards. Compartmentalized and labeled rooms make maintenance simpler and enhances safety for unprecedented accidents.

New legislations also support the requirement for compartmentalization. Ships are required to have at least a duplicate of equipment and at least two separate spaces for engines. So, what about these engines? Why are they so important and why do ships need so many of them?

Power and Engines

Just to answer those questions, we’ll have to visit more fundamental questions such as: How do the engines power a giant cruise ship? How does it help the ship propel forward? Are there specific engines that power different parts of the cruise? Out of many questions regarding the engines, the answer starts with the main engines.

The main engines are the engines that produce the majority of the power for the cruise ship to move. Depending on the type of vessel, the main engine connects to different parts of the propelling power. From traditional steamboats, to diesel electric, the engine is the fundamental powerhouse for the entire ship on the sea.

The following table is a general overview of how engines on different types of vessels are connected to the ship’s requirements.

Types Connected to
Conventional, Direct Drive, and Diesel Propeller Shaft
Diesel Electric Main Generators

So How Do These Engines Make the Ship Move?

As shown in the table, depending on the vessel type, the engine will provide power to different aspects of the ship. More or less, everything is distributed to operating proportions, but the key mechanics differ from one to another.


Diesel may be something more familiar to what we saw in old movies with steamboats. Even in modern days, we use similar mechanisms, if not labeled the same. The main difference is the source of pressure, which can be the traditional steam, or a fuel ignition.

Whether it is steam (traditional) or fuel ignition, the pressure generated from either push the pistons up and down in the vessel. These pistons connect to crankshafts through gears, which turns the pistons.

The crankshaft connects to the propeller through a long propeller shaft and gears, which further determines its speed in traditional diesel-powered vessels by steam pressure. Generally, the faster the pistons move up and down from the pressure, the quicker the propeller shifts would move.

With modern designs that control the propeller speed, engineers placed the gears in between the propeller and the engines which further enhances efficiency for both engines and propellers.

Again, although the majority of the engine provides electricity to the propeller shaft, electricity must be provided to the rest of the ship for entertainment. Often, options such as a shaft generator offer power to outlets such as lighting the dining and general appliances onboard while in motion.


Diesel-electric is another form of vessels that are found commonly with conventional diesel vessels. Unlike the conventional diesel, diesel-electric engines are connected directly to the generators that provide the electricity for the propellers and main generators.

This electricity also provides direct power for the ship’s lights, appliances, and much more.

Environmentally Friendly Power

On a side note, if the thought of diesel in the ocean disturbs you, there is some good news! Thankfully, more and more environmentally friendly options are appearing for cruise ships. For example, liquified Natural Gas (LNG) is an alternative method for powering ships that burns natural gas for power.

Using natural gas could reduce nitrogen oxide and carbon dioxide emissions significantly! With green-oriented companies, more green cruises have been released in the past few years.

That being said, if you are looking to book a trip, be on the lookout for green cruising opportunities! Onboard, you can also find environmentally conscious crew members and less-waste policies.

Source: CruiseCritic, Windstar Cruises, Green Cruises

Fuel Consumption

So, how does fuel play a part in powering the engine and the cruise ship? Let’s go back and visit what an engine does. An engine generates electricity to the propellers by supplying power the propulsion motors. How do they get the electricity and what makes an engine work? Most likely fuel and ignition (besides the steamboat example from before).

How much Fuel?

In general, a large cruise ship can consume up to 250 tons of fuel a day, which is close to 80,000 gallons a day. For medium size cruise ships, consumption can still range up to 150 tons of fuel a day.

Onboard, a ship may carry up to 1 to 2 million gallons of fuel, depending on the vessel size. Most of the power, which can be close to 85%, goes to the propellers, while the rest goes to keeping the cruise lit and comfortable for the passengers and crew members.

While passengers dine and enjoy their cruise aboard, crew members are constantly maintaining the proper fuel levels and providing proper power for the ship. As for the captain of the ship, he also has several variables to keep in mind to control fuel consumption and safety.

Fuel consumption may vary for several reasons, just like when we are driving our cars (but with more variability). For example, depending on where the wind is hitting the ship, the fuel consumption can go 1 – 5% over the average consumption rate.

Here is a short list of variables that the captain is keeping track of:

  • Speed of the cruise
  • Sea conditions (vs. sailing direction)
  • Weather (including the direction of the wind)
  • Distance
  • Size of the ship
  • Engine (Gas turbines, diesel-electric, diesel, or electric)

Source: Windstar Cruises, Cruise Mapper

Overall, the fuel, power, and engine, are all functions of making the magic happen. Starting from the design of the engine, to the crewmembers and captain maintaining the fuel and power consumption, a lot of action happens behind the scenes while passengers are onboard during vacation.

Floating and Buoyancy

Now that the ship is powered, how do we ensure that it floats? How do these massive machineries, ice-skating rinks, restaurants, and bars float on water while keeping thousands of passengers safely onboard?

While the cruise ship constantly pushes the water out of its way when moving forward, the water being pushed will try to come back to its place. This displaced water pushes back with a force on the vessel which lets the cruise ship stay afloat.

This is the general idea when engineers designed the hull of the ship. This ratio has to be calculated when designing a ship and has to be correct. If you get a chance to see the hull of most ships, they have a wide U-shape hull at the front to maintain the displacement.

In addition to basic buoyancy principles, an engineer must also consider the ship’s average density. This means that the ship’s general open spaces must be considered on top of the vessel’s average weight, so the vessel remains “less dense” than the ocean’s (usually salty) water. A great example is a rock sinking vs. a beach ball floating on water.

Source: Express

Water Onboard

So the power, fuel, engine, and buoyancy are the fundamentals of the ship. What about the details of the cruise ship such as the water in your shower? Is it salty? Is it fresh? Where and how does that come to your room without running out.

In general, most cruise ships have a steam-evaporation system. Water is pumped and desalinated before going to your room. During this process, your water is distilled and desalinated using a reverse-osmosis system and filtration system.

Distillation and desalination process uses a purification system to take all contents out of the water. This is generally not healthy to drink, so this water is mineralized and chlorinated for taste and safety.

Additionally, some ships have water brought onboard for laundry and other maintenance purposes. Generally speaking, the water onboard available for drinking are tested and checked for purification. If you are ever in doubt, check with a crew member to ensure the water is safe for consumption.

Is the Water Safe?

The answer to your ultimate question is, no, the water you are drinking is not toilet water. Regulated by the Maritime Organization laws, all “toilet water” must be treated and discharged into the ocean at a specific distance from the land. This water is never treated and recycled for passengers to use again.

On a side note, if you feel uncomfortable drinking this water, bottled water will most likely be available onboard for purchase. If you need special water for medical needs, you will most likely be able to bring a few bottles on board by notifying them ahead of time.


Now that we have reviewed how cruise ships work mechanically, let’s dive into the ship’s logistics. How do they work? Who’s working, how is it supplied, and how are they so cheap? Or perhaps, why are they so expensive? All of these questions come down to logistics.

General Logistics

Depending on your opinion and type of cruise you may have signed up for, you may think that your cruise is way under or over-budget. The cruise companies measure these decisions and prices to minimize cost and maximize returns (of course).

For example, cruise ships avoid fines by taking specific lines. They must often save fuel and hiring a knowledgeable captain who can make these decisions and keep passengers aboard safe is essential.

So, what are the different divisions of a cruise vacation? Are some better than others?

Mainstream, Premium, and Luxury

If we broke down cruises into 3 main categories, we could look at the mainstream, premium, and luxury lines of cruise types. You will often see categories within each of these types, but let’s break them down into the major categories for simplicity.


First, we will start with the mainstream cruise lines. These are cruises that are readily available, common, and well-known by the public with reasonable ticket costs.

Generally, these cruises’ primary business is through the onboard casinos, spas, shopping, and drinks. They suit the needs of most passengers. To make maximum profit, companies design these cruises by providing readily available entertainment on board. Most passengers are estimated to use 500$ onboard for their vacation experience.

Onboard, you will find general amenities, restaurants, bars, pubs, nightclubs, shopping, theaters, cinemas, swimming pools, gyms, karaokes, libraries, and even museums! These are great for big parties and are generally the biggest ships at sea.

Examples of Mainstream Cruise Lines that are known as “floating resorts”:

  • Carnival Cruise Line
  • Royal Caribbean International
  • Norwegian Cruise line
  • Disney
  • Lindblad Expeditions
  • Amawaterways

Mainstream cruises are great for

  • Group of friends
  • Families

Source: NancyandShawnPower, Fodors, and Wind Rose Network


Premium lines are perfect for adults or those that are retiring. The brilliant catch is that many have policies of “no kids allowed,” making it an excellent selling point for adults who need some peace and quiet. These cruises make money upfront by offering more access to ports and offering the serene luxury.

Premium cruises generally have a refined style in comparison to mainstream cruise lines. Activities are more focused on lifestyles. For example, you may find computer classes or a language-learning class. Besides, these ships still offer resort-style pools, game nights, bingo, spas, gyms, and maybe even a jazz night.

The perks for a premium in comparison to the mainstream is the higher quality of cuisine. Usually offering specialty restaurants and quality chefs, the price may be higher, but the overall quality is higher. The rooms at premium cruise lines are also superior, often offering suites and rooms with balconies.

Examples of Premium Cruise Lines

  • Princess Cruises
  • Celebrity Cruises
  • Holland America Line

The popular audience for Premium cruise lines:

  • Older Adults
  • Sometimes family-oriented

Source: Fodors


Luxury lines are pricier yet offer the best-selling point, fewer people onboard with a luxurious experience from beginning to end. The more expensive tickets provided to only a few hundred passengers make a profit for the company with the much higher ticket prices.

There are abundant space and a deluxe ship that will greet you as a valued guest from beginning to end for the high price. No doubt, one will fall for such an exquisite experience that starts from fine dining of caviar and foie gras to personal service available at one’s fingertips.

Course meals are offered from a full restaurant menu in your stateroom and served with limitless wine. Most interiors are luxurious and elegant, with rooms that are large and overlooking the sea.

Amenities range from gyms, spas, pools, and low-key entertainment. Generally targeting a niche group, most luxury cruise lines do not allow children.

Examples of luxury cruise lines:

  • Windstar Cruises
  • Paul Gauguin
  • Silversea Cruises
  • Crystal Cruises
  • Oceania Cruises
  • Ponant

Source: Cruise Critic

Many corporations own several of these different targets to make the most profit. Additionally, by corporations owning various cruise types, they can also hand down older ships throughout their other brands.

Logistics throughout the year

In addition to managing several types of cruises, there are numerous ways cruises have to operate to maintain their profits and not waste money through resting and selecting the wrong routes.

For example, cruise lines generally have high sales in November through April by Americans. The cold Americans usually take a warm vacation away from winter for a trip to the Caribbean.

What about other times of the year? Staying on seas without business is a considerable loss in revenue and usually unheard of. So, what do they do? They sell repositioning one-way tickets in April!

Generally, towards the end of April, you will start seeing two-week trips from the Caribbean to Europe. Typically, these trips can range from any state on the Eastern Coast of the United States to European countries.

Switching over/Cleaning

When there are one-way trips, there also needs to be exceptional coordination for a short turnaround between trips. When the cruise ships get to the destination, all hotels, theaters, dining, laundromat, and parks are cleaned and reset for the next people to come on board within half a day!

How do they do it?

During night-time, luggage and bags are ready ashore for passengers to check out. Meanwhile, all the trash is dumped, and the trash containments are cleaned, crew members switch, fuels are refilled, and food is refreshed with new inventory.

Remember the 1 to 2 million gallons of fuel to refill? This process, called bunkering, is a whole-team effort and is completed before the ship is ready to travel again.

A small boat, a “barge,” brings fuel to the 400 ports fueling for ships.

  • Barge secures to the side of the cruise ship
  • Connects a hose between the ship tanks
  • Pumps fuel while watching guard

When passengers load off, then the cleaning crew comes to clean the rooms. While the ship is pampering, they complete paperwork from the first trip, fulfill any necessary maintenance, redecorate rooms, and start preparing and cooking food and lunch for the next set of passengers coming on board.

Soon, the ship is reloaded with happy passengers and starts to move again. They make their profits from when the Casinos start, and food is served.

Crew Members

This brings light to the less noticed crew members. The ones that make all the magic happen. Generally, a cruise will have 1 crew for 2 passengers. Most of the crew members are working very long hours for several months.

In general, these crew ships are in their rooms when not on duty and do not get in the passengers’ way. How do cruises afford these crew members and their extended hours of work? The trick is that cruises can register in any country to abide by their labor laws. This is how they keep costs low, but there is a catch to that.

Crews and Destination

So, there is a catch, but it impacts your travel too. Did you ever wonder why cruises took less than expected stops? Not necessarily detours or emergency stops, but maybe a cruise led you to Ensenada or the Tabuaeran. This is due to the Passenger Vessel Services Act of 1886.

Why do cruises take weird detours?

Generally, a cruise ship can register any Labor law, as stated above. This makes it easy for cruise ships to pick a non-American country since it is cheaper and easier to fulfill (for business purposes). Unfortunately, if they choose this option, they must also abide by the Passenger Vessel Services Act of 1886. This act states that “No foreign vessel shall transport passengers between the United States.”

This means that if the cruise ship is registered under another country, they can never directly stop at an American stop if their initial take-off was in the United States. This is why you see stopes in Ensenada, for example.

For example, before Norwegian registered as American, if their cruise trip was to Hawaii from the motherland, they had to stop at Tabuaeran, a small island nearby.

When Norwegian registered as American, this let them bypass the Passenger Vessel Services Act. Unfortunately, this led the crew members’ service fees to rise, which led to higher ticket prices. If you want to watch how the above logistics work, check out this video!

A Cruise Ship Overview

Starting from the engine, fuel, and engineering to the logistics of companies, crewmembers, and governing policies, a cruise ship works in a marvelous way to shape every passengers’ experience abroad.

Thousands of crewmembers across various cruise ships, engineers of several centuries, and many hours of dedicated personnel make a cruise vacation work. Next time you are enjoying a cocktail on deck, remember that there is so much more behind the meaning of your cruise. There are so many parts that worked to make it happen! Enjoy and bon voyage!