If you’ve ever looked down at the hull of your cruise ship, chances are you’ve seen a variety of cryptic markings and symbols clustered near the bow and stern of the ship. Every one of these is an essential marking on any vessel, but what do they mean?

Mariner of the Seas boasts a striking profile. Photo © Aaron Saunders

The Plimsoll Line is where the ship’s superstructure paint meets the ship’s underwater anti-fouling paint. Aboard Mariner of the Seas, seen here in Cabo San Lucas, the Plimsoll Line is represented by the blue paint seen near the water. Photo © Aaron Saunders

Let’s take a look at some of these symbols and find out what they’re telling you. I can guarantee you will impress no one with this information, but I did win a cruise ship trivia game once by knowing one of them, so you never know…

Load Line Markings

Load line markings, like this one aboard Silversea's Silver Explorer, are used to designate the legal load limit of the ship in different waters. Here, the letters LR indicate she was surveyed by Lloyds Register. Photo © 2013 Aaron Saunders

Load line markings, like this one aboard Silversea’s Silver Explorer, are used to designate the legal load limit of the ship in different waters. Here, the letters LR indicate she was surveyed by Lloyds Register. Photo © Aaron Saunders

Easily the most cryptic marking you’ll see on the hull of your cruise ship is the Load Line marker. Typically located amidships, this marker is placed near the Plimsoll Line, also known as the point on the hull where the superstructure paint ends and the undersea anti-fouling paint begins.

This line of paint isn’t arbitrary, either – it denotes the maximum draft of the ship and the legal International Load Line limit. In layman’s terms, if you look down at your cruise ship and don’t see blue or red paint where the ship meets the water, you have a problem.

Each ship has a Load Line marker that consists of a circle with a line through it, bookended by two letters. These letters refer to the classification agency that surveyed the ship’s load line. The letters LR, for example, refer to Lloyds Register; BV for Bureau Veritas; RI for Registro Italiano Navale, and NV for Det Norske Veritas.

The Bulbous Bow

The bulbous bow of the Disney Wonder can be clearly seen under the water in this photgraph. The marking indicating it can be seen on the left-hand side, on the black portion of the hull. Photo © Aaron Saunders

The bulbous bow of the Disney Wonder can be clearly seen under the water in this photgraph. The marking indicating it can be seen on the left-hand side, on the black portion of the hull. Photo © Aaron Saunders

All the way at the front of the ship, the first symbol you’re likely to see is this one, warning that the ship has a submerged bulbous bow that protrudes from the front of the vessel. The bulbous bow improves the flow of water over the bow, and improves fuel efficiency.

Thrusters

Hurtigruten's Midnatsol has three bow thrusters, as indicated by the three symbols affixed to her bow. Because of the nature of her itineraries, she has more thrusters than a typical vessel of her size. Photo © 2013 Aaron Saunders

Hurtigruten’s Midnatsol has three bow thrusters, as indicated by the three symbols affixed to her bow. Because of the nature of her itineraries, she has more thrusters than a typical vessel of her size. Photo © 2013 Aaron Saunders

Located at the bow and the stern (if applicable), these circular symbols with an X through them designate the position of the ship’s thrusters. The number of the symbols also reflect the number of thrusters; if there are four symbols spaced evenly apart at the bow, your ship has four bow thrusters. If there is only one, your ship has only one.

At the stern, thrusters are only necessary if your ship has traditional rudder-and-screw propulsion. If your ship has azimuthing propulsion (large, outboard-style screws that can rotate 360 degrees in any direction), your ship doesn’t require thrusters at the stern.

Propulsion

Symbols at the stern of MSC Poesia indicate the ship has two stern thrusters, and is driven by traditional screw-and-rudder propulsion. Photo ©  Aaron Saunders

Symbols at the stern of MSC Poesia indicate the ship has two stern thrusters, and is driven by traditional screw-and-rudder propulsion. Photo © Aaron Saunders

A set of symbols near the stern of your ship will tell you that your ship’s screws, or propellers, are mounted underneath. While most vessels have stern-mounted screws, some ships – like double-ended ferries – have screws mounted at the bow and the stern.

From the Deck Chair will return with less-geeky cruise coverage tomorrow. We promise.

 

13 Responses to Cruise 101: Know Your Hull Markings

  1. Ralph McDowall says:

    Please refer to Wikipedia to see what a plimsoll line is. The plimsoll line is not the painted water line.

    • Aaron Saunders says:

      Hi Ralph,

      The Plimsoll Line is where the hull of the ship meets the surface of the water – in concept or reality. The easiest way to describe that to people is to refer them to where the ship’s hull changes colour from the superstructure paint to the anti-fouling paint. The Plimsoll Mark is the load limit sign shown on the photograph of the Silver Explorer.

      • J K Williams says:

        Sorry Aaron, but you are incorrect sir. The plimsoll line is the same as the load limit line. The physical hull depth limit in the water is indicated by the plimsoll mark. The demarcation line between the upper and lower hull is the water line. The lower hull is not necessarily painted in anti-fouling paint. The lower hull on many large commercial vessels is simply red lead paint. Anti-fouling would generally be cost prohibitive due to the large hull size, unlike private vessels.

        Since your page was intended to educate people on hull markings, you forgot to include draft markings!

        • Aaron Saunders says:

          Thanks for the information – I think I may have to do a follow-up article now!

        • Alan Gideon says:

          1. On the Plimsoll mark, the multiple horizontal lines indicate the load limits for different “types” of water, i.e, winter, summer, fresh, etc. since they all have different densities and therefore different abilities to create buoyancy.
          2. “Red lead” paint is an old fashioned primer. It was never intended to be a finish coat. I believe you may be confusing red lead paint with the copper-based antifouling paints that ships used to use. Current international law prohibits the use of most copper-based bottom paints, which is why most companies have changed to ablative or epoxy type paints. The reason for painting the bottom, aside from preventing rust, is to discourage marine growth. Modern paints prevent barnacles and such from attaching themselves to the ship’s bottom rather than poisoning them as in the past.

  2. Thank you so much for this! I always wondered what these markings meant and I’m so glad you took the time to explain them. Interesting!

  3. Nicholas Sabalos says:

    Absolutely love some “Geeky” ship talk! Pure gold to the ex-ship-driver in me! 🙂

    A column on ship horn signals and flags might be helpful to many at some point. I’ve found most passengers clueless about what one-long-three short blasts means.

    Perhaps if passengers knew more about the wonders of the modern engineering marvel in which they are sailing, they might be more understanding and appreciative of just how much work is involved in delivering their “luxury cruise” to them without nary a hitch!

  4. […] While at anchor, Zodiac’s Chris, Jeff and Captain Tim even brewed a batch of Zodiac’s own “Schooner Rat IPA”, which will be ready for sampling on the October brew cruise later this year. Past brews have included the clever “Plimsoll Line IPA” with the tagline, “It’ll Get You Loaded.” For a look at why that’s so funny, click here. […]

  5. Andy King says:

    I may be able to provide some further information as I am a Naval Architect and work for a Classification Society. My department is directly involved in the approval and application of Load Line marks. The term ‘Plimsoll’ line is an outdated term for the Load Line mark and is not the name for the waterline (or what may be perceived to be the change in paint colour). Indeed, the actual waterline continually changes due to the loading condition of the ship – for a cruise ship, this changes as Fuel Oil and Fresh Water is used up and additional liquids or supplies (or passengers) are taken onboard. The ‘Plimsoll’ reference comes from Samual Plimsoll who first proposed the idea of a loading limit in order to improve ship safety and avoid overloading. The Load Line mark can never be immersed and is actually determined from the required freeboard (distance from the Load Line mark to the deck edge marking above) and not the required draught (distance from the mark to the bottom of the vessel underwater). As a result, you will see a small horizontal marking some distance above the Load Line and this is the Deck Marking – the upper freeboard measurement point. The round circle with the line and the two letters of the assigning authority is the Load Line mark and then the Load Line Grid is the additional markings for the varying waters – varying by density, oceanic region and yearly season. The Load Line mark and grid must be physically marked on the ship using welded plating (or similar), it cannot simply be painted on. A ship can have multiple load lines depending on different cargoes and routes but only one Load Line can be marked on the side of the ship on at any one time. As well as the Load Line draught (the maximum loading draught of the vessel), there is also an assigned Scantling Draught – this is always above the Load Line draught but is not marked on the ship and is the calculated maximum draught for the structural aspects of the ship.

    • Aaron Saunders says:

      Thanks for the fantastic comment, Andy! You’re a wealth of information. Best regards, – Aaron

  6. Andy King says:

    In terms of the change in paint colour, this is largely down to anti-fouling coatings as previous writers have said. Lead paint is definitely not allowed – the International Convention on the Control of Harmful Anti-fouling Systems in Ships prohibits harmful anti-fouling paints as some compounds can adversely affect marine animals. Today, the underwater coating is defined by needing to minimise marine growth of barnacles and other organisms, minimise corrosion and also lower resistance and improve fuel economy.

  7. Andy King says:

    Lastly, one other sign you may see on a ship’s side is a box with TUG marked in it. This is the strengthened points of the hull where tugs may push the vessel.

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