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What is a cruise ship dry dock?

22 Aug 2022
Jenna DeLaurentis

Royal Caribbean cruise ships undergo a dry dock every few years for routine maintenance and refurbishment, but why are dry docks necessary and how does the process work?

Harmony of the Seas in dry dock

Whether you've read about it online or heard from another passenger or crew member about a ship's upcoming dry dock, you might be wondering what this entails.

Just like when your car needs to get service and they hoist it up on a lift, cruise ships need to get "under the hood" work done to keep them working properly.

What is a cruise ship dry dock?

A dry dock is a narrow basin that can be filled and drained of water to allow for maintenance and repairs on a ship’s hull.

Because the hull remains underwater at all times, it’s necessary to remove the ship from water occasionally to clean the hull and work on routine maintenance of the ship. Royal Caribbean ships usually have dry dock once every five years.

For a ship to enter a dry dock, the basin must first be filled with water, allowing the ship to sail in safely. Once the ship sails into the dry dock and is situated in the correct position, the gate is closed and water is drained.

Dry docks are also used during the construction of new ships. Because ships cannot, of course, be constructed in the water, they are constructed on a dry dock which can later be filled with water to allow the ship to safely sail out once constructed.

What type of maintenance and repairs happen during a dry dock?

During dry dock, ships undergo routine mechanical work as well as checks of the ship’s propeller blades, thrusters, stabilizers, navigation software, etc. If anything needs to be replaced, it will be replaced during this time. The ship’s hull is cleaned during dry dock with a power washing system and typically repainted.

Parts of the ship’s exterior and interior spaces are also repainted during dry dock. When Harmony of the Seas underwent dry dock in 2021, for example, the shipyard estimated they would use around 8,000 liters of paint on the ship!

Dry dock is also a time for interior refurbishments such as adding new coats of paint and replacing flooring, bedding, curtains, etc. Anything that cannot easily be done while a ship is in service will be done during dry dock (deep cleaning of onboard spaces, adding new venues, etc.).

Why does the ship’s hull need to be cleaned?

If routine cleaning of a ship’s hull is neglected, it can lead to the accumulation of marine line on the hull, known as biofouling. Barnacles, shellfish, algae, and other marine life can live on the hull.

The most notorious are barnacles, a crustacean related to lobsters and crabs, who must attach onto a hard surface to develop into adults. In fact, the natural “glue” barnacles use to attach to a ship’s hull is so strong that researchers have been trying to mimic the sticky substance for use commercially and medically.

This, of course, causes a few key problems for ships. First, a buildup of marine life can cause more drag, making the ship’s speed lower, which increases both fuel costs and carbon emissions.

It also means that marine life can be transported from one area of the world to another, causing potential environmental impact as existing ecosystems may be affected by new types of marine life.

Therefore, having routine dry dock maintenance to clean the ship’s hull can help negate this problem and assure that large buildups of marine life do not occur on Royal Caribbean’s ships.

Refurbishments and amplifications

Mariner of the Seas in dry dock for her 2018 amplification

During some dry docks, Royal Caribbean ships will undergo significant refurbishments or amplifications through Royal Caribbean’s Royal Amplified program.

Royal Caribbean uses two terms for upgrading its cruise ships: refurbishment and amplification.

Refurbishments are smaller enhancements to a ship, such as upgrading staterooms, re-designing an existing venue, switching a specialty restaurant, etc. Amplifications are more in-depth refurbishments where Royal Caribbean “amplifies” an older ship with many of the popular features found on the fleet’s newest cruise ships. 

Related: What was added to each Royal Caribbean ship during its Royal Amplified refurbishment

Amplifications may include adding water slides, new staterooms, renovated pool decks, several new bars and restaurants, and activities like an escape room, laser tag, and bungee jumping.

Dry docks take cruise ships out of service for around two weeks for routine maintenance, but amplifications can take over a month.

When Oasis of the Seas received her amplification in 2019, which included adding waterslides, the Ultimate Abyss, a Caribbean resort-style pool deck, and new dining venues, it took a total of 63 days.

In fact, when Oasis of the Seas was amplified, nearly every single venue was touched by workers to either repair, enhance, or alter the space. About 800 tons were added to the ship when all the work was done.

Every day counts in a dry dock

When a cruise ship needs to go into dry dock, it means the ship will be out of service and that means no revenue for that time.

Similar to how a professional athlete that is injured cannot help the team win, a cruise ship that goes in for work will not improve the cruise line's bottom line.

Oasis of the Seas dry dock overhead

Over 2,700 contractors were onboard Oasis while the ship was in dry dock in Cadiz, Spain to get the work done in time.

Oasis was out of service for 63 days in order to get all of her work done, which is a significant investment by the cruise line. The amount of time would have been far less had they not decided to upgrade the ship, but the short-term financial impact is offset by the higher revenue and increased bookings down the line when the ship returns to service.

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Jenna DeLaurentis enjoys exploring new ports of call around the world on a cruise ship, learning about new cultures, discovering beautiful landscapes, and trying diverse cuisine. She loves to get active while at port, whether cycling through mountains in the Caribbean or scuba diving under the sea.

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