cruise ship hull markings

Ship Hull Markings – 7 Major Markings For Most Of The Ships

You might have spotted the symbolic representation and alphabet regardless of their dimensions and location on different vessels. These ship hull markings may seem familiar to us, yet often, they go unnoticed or not completely understood.

These symbolic representations tell something specific about a certain region in a vessel as well as certain key aspects related to the vessel for those in the operational area must know.

 Also, these symbols are mandatory as per laws put forward by the ship classification societies . Let us deepen our knowledge from the below sections.

What Are The Main Ship Hull Markings?

Some of the most seen markings on a vessel are either placed to represent a specific function or a means of safety standards. The main symbolic representation corresponds to the loading of the vessel which was used from the early days of maritime transportation .

Looking back into history, the Kingdom of Crete is credited with developing the first recognized marine loading standards in 2500 BC.

Different regions around the world had different rules, for example, considering only Italy as an example Roman maritime rules had their set of standards, Venice required a cross to be marked on a ship’s side during the Middle Ages, and Genoa needed three horizontal lines.

Some of the most found markings are the following,

• International load line marking
• Draft marking
• Bow thruster marking
• Tug/no tug marking
• Pilot boarding marking

Let us look into each of these kinds of markings.

International Load Line Marking

The Plimsoll Lines or International Load Lines are probably the symbols that are the most significant and commonly found on all the vessels. The circle with a horizontal line through it is the original Plimsoll Line.

Plimsoll Line was created in 1876 by Samuel Plimsoll, a member of the British Parliament, after the loss of a vessel and her crew as a result of deliberate cargo overloading by dishonest merchants who over-insured their vessels and then preferred to see them complete her mission.

The International Load Line markings are found close to the center of the hull and indicate how far below the waterline a ship’s draft (the distance between the waterline and the bottom of the hull) may be governed by a variety of conditions, including fluctuations in water temperature and density.

Let us consider a large container ship that is being loaded while it is in port. The ship sinks further into the ocean as the weight and number of cargos increases. The ship would be at serious risk of sinking if the freeboard—the gap between the waterline and the top of the hull—became too small.

The following is a graphical representation of a typical load line marking.

The ship’s registration authority, in this case, the Lloyd’s Register of Marine Shipping , is indicated by the letters “LR” on either side of the Plimsoll Circle.

Draft Markings Or Draft Marks

Draft markings are numbers placed in a vertical line towards the forward and aft of a vessel. They gauge the distance (draft) between the waterline and the lowest point on the ship’s hull, which fluctuates depending on cargo loading.

By comparing the waterline depths on the ship’s two sides, the number at the waterline may be used to determine the ship’s draft, if it is overloaded, unevenly loaded, and trimming heeling.

Bow Thruster Markings

The bow thruster markings are a circle with an “X” inside or propeller visualisation. It denotes a bow thruster located at that specific region, which helps a ship’s bow be moved laterally. When un/docking, this becomes helpful.

Similar to those seen at the bow, markings may also be seen at the stern of the hull. Instead of the conventional propellers on shafts and a rudder , many contemporary cruise ships use azimuth pods, hence they lack an aft thruster.

A vessel with bow thruster markings symbolizes the use of thrusters and the vessel will be using a conventional propeller and thruster system for maneuvering. To prevent harming both the ship and the tug, tugboat captains avoid both concealed bow thrusters and bulbous bows.

Bulbous Bow Marking

This marking represents that the ship has a bulbous bow , which is a bulging bulb at the front of a ship that may be wholly underwater when the ship is fully loaded, as shown by the symbol that resembles the number “3,” which is used to indicate this. A large value of resistance of a vessel is decreased by a bulbous bow by producing its wave, which partially cancels out the ship’s bow wave.

Tug/No Tug Markings

Other marks which include only alphabets may be seen around the center of the hull and are just as significant as those at the bow and rear.

Shell doors, also known as service access doors and hatches, are secured by marks like “No Tug,” as can be seen below on a Celebrity ship. Shell doors offer access to service ways for loading and unloading food, freight, and machinery.

Also, areas, where tugs are allowed to be in proximity of the vessel, are indicated with the help of an indication written as “Tugs”.

Pilot Boarding Marking

A white square shape with a yellow boundary indicates a specification location on the hull where pilot boats can pull up next to a moving vessel, where there is a specific entry point through which the pilot can board the vessel.

A general overview of all the markings is given in the diagrammatic representation below to make it much easier to visualize the same the next time you come across any vessel.

Why Is International Load Line Marking Relevant For Vessels?

Let us take a typical example, say a cargo vessel is plying in a temperate region, like England, the original Plimsoll Line functioned best while loading a ship in summer waters.

Today, the letter “S” stands for Summer. Later, additional letters were added to account for the various buoyancies of water in various climatic regions of the planet.

The ocean is indicated by the letter “T” for tropical sea water, “S” for summertime temperate, and “W” for wintertime temperate regions to the right of the vertical line.

The saltwater of the winter North Atlantic is indicated by “WNA” below “W.” For freight loading, a ship in “F” temperate fresh water, and “TF” tropical freshwater, use the letters to the left of the vertical line.

Looking into the properties of water, salt water is denser than freshwater, Warm water is less viscous than cold water, whether it is fresh or salty. Density has a direct relation to buoyancy. So, even though the winter North Atlantic Ocean’s salt water is the most buoyant, only the smallest quantity of cargo is loaded there, per these load lines.

Now you may wonder why this is done so. A freighter could indeed be loaded (illegally) with more goods and yet have enough freeboard if it only operated from Stockholm to London during the winter. However, Plimsoll lines account for the whole possible range of a freighter’s voyage, not simply the location at which it is loaded.

The hull of the ship will continue to sink as the ocean heats if it travels from London to Brazil, which is extremely close to the equator. An overloaded cargo may not have enough buoyancy or freeboard to protect against the risk of large waves when it eventually reaches the outflow of the river deltas, where freshwater can spread as far as 200 miles into the oceans.

No matter where else the freighter travels in the globe, it will not come across water that is less buoyant than where it is right now, hence at Brazil, the freighter may be loaded until the ship’s hull sinks to the “TF” tropical fresh water line.

The ships are inspected by classification societies , who then calculate their load lines. The Summer Load Line is the name of the common reference load line. The symbol for this is a horizontal line passing through a circle.

After taking into account water density and temperature, further lines show the limit. On the Summer Load Line, the letters next to each occurrence of the load line correspond to the classification society and varying load restrictions in different seas, such as for tropical or North Atlantic operations.

Ship Hull Marking Summary

Thousands of commercial ships travel across international seas, carrying billions of tons of cargo annually and handling more than 80% of global trade .

The best people to observe and comprehend these hull symbols are tugboat captains and other people who are personnel in ports or on the sea. Now that you know more about the symbols the next time you are near a vessel you can pay more attention to these details.

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The Secret Language of Ships

Signs and symbols on the sides of ships tell stories about an industry few outsiders understand., authored by, article body copy.

Approaching the container ship in San Francisco Bay, the tugboat looks like a pit bull puppy chasing an eighteen-wheeler. When the vessels are an arm’s length apart, the ship’s mate throws down a line. Now leashed to the ship, the tug can push and pull it around the bay. Big ships can’t easily slow down or maneuver by themselves—they’re meant for going in a straight line.

Tugboat crews routinely encounter what few of us will ever see. They easily read a vessel’s size, shape, function, and features, while deciphering at a glance the mysterious numbers, letters, and symbols on a ship’s hull. To non-mariners, the markings look like hieroglyphs. For those in the know, they speak volumes about a particular ship and also about the shipping industry.

Oceangoing vessels carry over 80 percent of the world’s trade, with more than 90,000 merchant ships plying international waters. Tankers, bulk carriers, and container ships—the largest things on Earth that move—are by far the most important modes of transportation of our time. They convey billions of tonnes of goods every year, bringing us everything from cars to crude oil to containers jammed with fidget spinners.

Those who work in ports or on the water have a good view of the proceedings; tugs may have the best view of all. These photos get you closer to ships than most people will ever be.

“The sides of ships have their own sort of beauty,” says photographer David Webster Smith, who is also a San Francisco tugboat engineer. “As soon as I can, I get my camera out.”

Most ships have clues to their identity emblazoned on their stern, often in the same order: owner, name, port (or “flag”), and International Maritime Organization (IMO) number. American President Lines (APL) owns this ship, christened the Mexico City , and it sails under the flag of Singapore.

The owner, name, and flag may change over a ship’s lifespan, but the IMO number stays the same as mandated by an international maritime treaty. Like vehicle identification numbers, IMOs help thwart fraud. Do a web search on an IMO number and the ship’s full history pops up.

Curious about those yellow-green, fortune-cookie-shaped objects along the lines? They’re anti-rat devices, foiling rodent attempts to scrabble from dock to line to ship.

Why would a ship owned by a South Korean company (Hanjin) list its port as Panama?

More than 70 percent of the world’s commercial ships sail under what’s called a “flag of convenience.” This means that the ship is registered in a foreign country and sails under that country’s flag, usually to reduce operating costs, sidestep taxes, or avoid the stricter safety standards of the owner’s country.

By far the most popular flag of convenience is Panama, with Liberia and the Marshall Islands fast gaining ground. For these countries, the fees companies pay to fly their flags are a significant source of revenue.

There’s another thing about this ship worth mentioning. See the crew members up on deck, at the far left and right of the photo? They’re actually dummies dressed as mariners, meant to fool pirates into thinking someone is always on watch.

These marks, called load lines, show the maximum load a ship can carry.

Load lines owe much to a British member of Parliament named Samuel Plimsoll. Worried about the loss of ships and crew members due to overloading, he sponsored a bill in 1876 that made it mandatory to have marks on both sides of a ship. If a ship is overloaded, the marks disappear underwater. The original “Plimsoll line” was a circle with a horizontal line through it. The symbol spread around the world; additional marks were added over the years.

The letters on either side of the circle stand for the ship’s registration authority. AB is the American Bureau of Shipping, one of 12 members of the International Association of Classification Societies, which sets and maintains safety standards for more than 90 percent of the world’s cargo ships.

The marks and letters to the right of the circle indicate maximum loads under different climatic conditions. Salt water is denser than fresh, cold water denser than warm. Since water density affects ship buoyancy, different conditions call for different load lines.

W marks the maximum load in winter temperate seawater, S in summer temperate seawater, T in tropical seawater, F in fresh water, and TF in tropical fresh water, like that of the Amazon River.

This ship is equipped with what’s called a bulbous bow, a protrusion low on the bow. Contrary to its ungainly appearance, the bulb actually reduces drag, increasing speed and fuel efficiency.

The white symbol that looks like the numeral five without the top line alerts tugboats to the presence of the bulb, which under certain conditions may be entirely underwater. Tugs need to be aware of the protuberance to avoid running it over as they maneuver around the ship, possibly damaging both the bulb and the tug.

The white circle with an X inside signals the presence of a bow thruster, a propulsion device that helps the boat maneuver sideways, a boon for getting on and off docks.

The numbers arranged in a vertical line—called draft marks—measure the distance between the bottom of the hull (the keel) and the waterline. If the water comes up to the 10-meter line, for example, that means 10 meters of the ship is underwater.

Where the water hits the draft lines tells sailors if the ship is overloaded, and—when compared to the reading on the opposite side of the boat—if it’s listing to one side.

To the left of the draft lines are different versions of the bulbous bow and bow thruster symbols. BT|FP tells you the position of the bow thruster: between the ballast tank (BT) and the forepeak (FP), the forwardmost part of the ship. It’s important for a tugboat operator to know the location of the bow thruster, as it creates turbulence that the tug would rather avoid.

Two tugboats approach an oil tanker near the Richmond-San Rafael Bridge. This photo is taken from a third tug that’s moving in on the ship, guided by white arrows pointing to “chocks” that house small but strong posts called “bitts.” The tug fastens lines to these bitts.

SWL 50t means that the safe working load for each bitt is 50 tonnes. Once the tug has fastened a line to the bitt, it will exert no more than 50 tonnes of pulling pressure as it helps the ship brake or negotiate docking.

Are these bird cubbies, rusting in the sea air? Not quite. The cavities are, however, known as pigeonholes. They’re part of an in-hull ladder that allows mariners to climb up the side of a barge. Unlike cargo ships, flat-bottom barges are not self-propelled. They’re usually towed or pushed by tugboats, though in the early days they were hauled up rivers and canals by horses, mules, or donkeys on an adjacent towpath. Though barges are often unstaffed, they occasionally must be boarded, for instance when a line needs to be thrown down to a dockworker. Pigeonholes give the boarders a leg up.

A ship’s paint job isn’t primarily about aesthetics or branding. When you see this two-toned effect, the paint closer to the waterline is often of a different chemical composition, one that holds up better to immersion. Even more than preventing corrosion, a hull coating that may be underwater has to guard against the slime, algae, and barnacles that cling fast to a friendly hull.

What’s so bad about shellfish and microorganisms hitching a ride? The crusting of barnacles, mussels, and bacteria—called biofouling—creates drag, slowing ships and upping their fuel intake by as much as 40 percent. Foreign species can also invade ecosystems and outcompete native species for food and space. To remove the hitchhikers, the ship goes into dry dock for scraping or power washing.

Enter preventive measures, like antifouling paint. Early iterations contained copper and even arsenic, which effectively poisoned the organisms but also the water. Modern antifouling coatings are more eco-friendly, and there are always new systems being floated, such as creating a hull surface that mimics shark skin, since, unlike some whales, sharks don’t tend to harbor barnacles.

The white rectangle edged in yellow—a pilot boarding mark—tells the maritime pilot where to board the ship. Maritime pilots (also called harbor or bar pilots) are experts on the navigational hazards of their home harbor and crucial characters in the drama of maritime life.

The pilot catches a ride out to the ship on a boat about the size of a tug, scrambles up a ladder hanging off the clifflike side of the ship, and takes over for the captain just before the ship comes into port. The rope ladder may not yet be deployed when the pilot boat approaches a ship, so the boarding mark is an important guide.

The white marks on the red are battle scars, reminders of scuffles with docks, other vessels (mostly tugs), and the sides of canals.

A maritime pilot would board this ship using the two ladders pictured. First, he or she ascends the rope ladder, sometimes called a Jacob’s ladder, alluding to the biblical Jacob, who famously dreamed of a ladder connecting heaven and Earth. Partway up, the pilot sidesteps onto the relative security of the diagonal gangplank, called an accommodation ladder.

Sometimes the pilot makes do with just the rope ladder. According to IMO regulations, if the distance from water level to deck (which changes according to ship load and sea conditions) is more than nine meters, the ship must deploy an accommodation ladder in addition to the rope ladder. Nine meters or more is a long climb on a rope ladder, especially under difficult sea conditions.

Boarding and disembarking are probably the most dangerous parts of the job. Getting off the ship, pilots may let go of the ladder and use what’s called a manrope to help them onto the deck of the pilot boat. That way they’re less likely to be crushed between the pilot boat and ship.

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Changing Colors: Major Cruise Brands Introduce New Liveries

• June 12, 2021

Cruise lines are embracing new hull art and ship liveries in an effort to stand out, as highlighted by Carnival Cruise Line and Royal Caribbean International, which are both embracing new paint schemes on their ships.

Carnival Cruise Line

This year Carnival Cruise Line became the latest brand to introduce a new livery. In May, the company announced that the new hull design of the new Mardi Gras will become a feature across the fleet as the company prepares to celebrate its 50th birthday in 2022.

The livery is highlighted by a stately navy-blue hull, inspired by officers’ uniforms, along with vibrant red and white accents running the entire length of the ship. 

After the Mardi Gras, the Carnival Magic (pictured above) was the first vessel to receive the new colors during a drydock in Marseilles.

Royal Caribbean International

Royal Caribbean International updated its livery in 2020, adding a larger name on the hull of the new Odyssey of the Seas . Unusually big, the vessel name runs 87.4 meters down each side of the ship.

It’s the second new look for Royal Caribbean in the last decade.

The Quantum of the Seas, launched in 2014, debuted a new color template for the company, with a light blue hull. 

The color scheme was later added on selected vessels, including the recently “Amplified” Freedom of the Seas.

Celebrity Cruises

As part of the Celebrity Revolution program , Celebrity Cruises is adding a new livery to its fleet. While undergoing the upgrades, the company’s existing ships also receive the color scheme of the new Edge-cClass vessels that have a dark blue hull.

The livery has been added to seven of the 11 Celebrity ships.

Princess Cruises

Princess Cruises introduced a new livery in 2016 , adding a giant version of its “sea witch” logo to the hull of the 2013-built Royal Princess.

The fresh look, which also includes the repositioning of the ship’s name, was later added to other vessels and is now present on the entire fleet.

Costa Cruises

In 2018, Costa C became another Carnival Corporation brand to introduce a revised livery . The subtle change saw the name of the ships painted on the bow with a specially designed new font in larger lettering, as well as the addition of a stylized Italian flag.

The livery was created to mark the 70th anniversary of the Italian brand and has since been added to the entire fleet.

With the introduction of the 2015-built Britannia , P&O Cruises also introduced a new paint scheme to its fleet.

The brand’s traditional funnels were repainted in blue, with the addition of P&O’s rising sun logo. As part of the new livery the hulls across the fleet saw a stylized British flag added.

P&O Australia

In 2016, P&O Australia announced the addition of a stylized Southern Cross to the hull of its latest vessel , the Pacific Explorer. Along with a new color and a new logo on the funnel, the five-star constellation image became P&O’s new livery.

More recently, the look was added to the Pacific Encounter , the newest ship in the fleet.

Silversea Cruises

Silversea is introducing a new hull color to its fleet with a light gray adorned on the hulls of select ships.

Three vessels are currently sporting the updated color scheme, including the new Silver Origin.

Under construction in Italy , the newbuild Silver Dawn already shows the new gray hull as well.

Marella Cruises

To mark the addition of the former Splendour of the Seas to its fleet , the TUI-owned Marella Cruises introduced a new livery in 2016.

Then called Thomson Cruises, the brand created a new “wave design”, in-line with TUI’s airplanes.

According to Marella, the new branding was meant to keep the consistency across all markets and is now present on the entire cruise fleet.

Fred. Olsen Cruise Line

In 2015, Fred. Olsen debuted a new look on its fleet.. The new color scheme and livery represented the change of position for its product within the premium market, the company said at the time.

The gray hull is a throwback to Fred. Olsen’s heritage, when the first Black Watch and Black Prince were launched in the 1930s, according to the company. The use of the “Cartier” red line refers to the company’s “Red Carpet” service level for every guest.

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