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Battling Barnacles

Short answer: Barnacles are crustaceans that cement themselves to hard surfaces, including ship hulls, as part of 'biofouling' along with slime, algae and other organisms.

A 2007 study by Michael Schultz of the US Naval Academy, modeling a mid-sized naval frigate, predicted that heavy calcareous fouling such as barnacles and tubeworms raises the shaft power needed at cruising speed by up to 86%. Even slime films brought significant penalties. Hulls are protected with antifouling coatings and cleaned in dry dock or in the water by divers and robots. In-water cleaning has its own risks. The IMO's 2023 Biofouling Guidelines warn it can damage coatings and release invasive species and toxic coating debris. They say heavier fouling should be removed with systems that capture the debris.

VideoWrite-up4 sources
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What should you know about Battling Barnacles?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. Heavy calcareous fouling can raise required shaft power by up to 86% (Schultz, 2007).

    DD-705-F01 · Write-up · Exhibit B (The drag penalty)

  2. The IMO revised its Biofouling Guidelines in July 2023.

    DD-705-F02 · Write-up · Exhibit D (Cleaning risks)

Video transcript: Battling Barnacles: Hitchhikers That Burn Fuel

DID YOU KNOW? Cleaning barnacles off ships is an important maintenance process because these hard-shelled marine organisms attach firmly to hulls and dramatically increase drag as a vessel moves through water. Even a thin layer of barnacles can raise fuel consumption by 20% or more by disrupting smooth water flow along the hull. Increasingly, specialized underwater cleaning robots and divers perform the work while the ship remains in port, using rotating brushes or high-pressure jets to strip away barnacles, algae, and other fouling organisms. NOW YOU KNOW!

Burned-in captions, read frame by frame (see transcript.md) · 26.8s Reel ·

Video coming soonBattling Barnacles · Instagram Reel
Battling Barnacles: Hitchhikers That Burn Fuel Instagram Reel · · 26.8s

The write-up

Hitchhikers that burn fuel. Heavy hull fouling can raise power needs by up to 86%.

  1. Exhibit A

    What fouls a hull

    Biofouling starts with a slime film of microbes and builds to 'macrofouling' such as barnacles, tubeworms and weed. Barnacles glue themselves on with a protein cement.

  2. Exhibit B

    The drag penalty

    Schultz's 2007 model of a frigate predicted that heavy calcareous fouling raises required shaft power by up to 86% at cruising speed. Light slime alone carried a smaller but significant penalty.

  3. Exhibit C

    Prevention

    Antifouling coatings slow growth. 'Proactive' cleaning removes slime before barnacles settle, and 'reactive' cleaning strips heavier fouling.

  4. Exhibit D

    Cleaning risks

    The IMO warns that cleaning can damage coatings and release harmful waste and invasive species. Its 2023 guidelines limit uncaptured cleaning to light fouling, below rating 2, in approved areas.

  5. Exhibit E

    Capture tech

    Newer robotic in-water cleaners use suction and filtration to capture debris, and researchers are developing tests of how much they capture, including with artificial barnacles.

Questions people ask about Battling Barnacles

What kind of animal is a barnacle?

Barnacles are crustaceans.

Source: Write-up · Exhibit A (What fouls a hull) · IMO: 2023 Guidelines for the control and management of ships' biofouling, MEPC.378(80); Frontiers in Marine Science (2024): Capture efficacy test method for in-water cleaning using artificial barnacles

By how much can heavy calcareous fouling raise required shaft power, per Schultz (2007)?

Up to 86% at cruising speed.

Source: Write-up · Exhibit B (The drag penalty) · Schultz (2007), Effects of coating roughness and biofouling on ship resistance and powering, Biofouling

Which body issued the 2023 Biofouling Guidelines?

The International Maritime Organization.

Source: Write-up · Exhibit D (Cleaning risks) · IMO: 2023 Guidelines for the control and management of ships' biofouling, MEPC.378(80); IMO: Biofouling

What's one risk of in-water cleaning?

It can release organisms and coating debris.

Source: Write-up · Exhibit D (Cleaning risks) · IMO: 2023 Guidelines for the control and management of ships' biofouling, MEPC.378(80); IMO: Biofouling

What usually forms on a hull before barnacles?

A microbial slime film.

Source: Write-up · Exhibit A (What fouls a hull) · IMO: 2023 Guidelines for the control and management of ships' biofouling, MEPC.378(80); Frontiers in Marine Science (2024): Capture efficacy test method for in-water cleaning using artificial barnacles

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. What kind of animal is a barnacle?

    1. A crustacean
    2. A mollusk
    3. A fish
    4. A plant
    Show the answer

    Answer: A. A crustacean Barnacles are crustaceans. Source: Write-up · Exhibit A (What fouls a hull) · IMO: 2023 Guidelines for the control and management of ships' biofouling, MEPC.378(80); Frontiers in Marine Science (2024): Capture efficacy test method for in-water cleaning using artificial barnacles

  2. By how much can heavy calcareous fouling raise required shaft power, per Schultz (2007)?

    1. Up to 8%
    2. Up to 86%
    3. Up to 300%
    4. Not at all
    Show the answer

    Answer: B. Up to 86% Up to 86% at cruising speed. Source: Write-up · Exhibit B (The drag penalty) · Schultz (2007), Effects of coating roughness and biofouling on ship resistance and powering, Biofouling

  3. Which body issued the 2023 Biofouling Guidelines?

    1. The IMO
    2. NASA
    3. FIFA
    4. The WHO
    Show the answer

    Answer: A. The IMO The International Maritime Organization. Source: Write-up · Exhibit D (Cleaning risks) · IMO: 2023 Guidelines for the control and management of ships' biofouling, MEPC.378(80); IMO: Biofouling

  4. What's one risk of in-water cleaning?

    1. Spreading invasive species
    2. Making ships heavier
    3. Freezing the hull
    4. Raising sea level
    Show the answer

    Answer: A. Spreading invasive species It can release organisms and coating debris. Source: Write-up · Exhibit D (Cleaning risks) · IMO: 2023 Guidelines for the control and management of ships' biofouling, MEPC.378(80); IMO: Biofouling

  5. What usually forms on a hull before barnacles?

    1. A slime film
    2. Rust only
    3. Ice
    4. Sand
    Show the answer

    Answer: A. A slime film A microbial slime film. Source: Write-up · Exhibit A (What fouls a hull) · IMO: 2023 Guidelines for the control and management of ships' biofouling, MEPC.378(80); Frontiers in Marine Science (2024): Capture efficacy test method for in-water cleaning using artificial barnacles

Cite this case file

Easterling, Marcus. "Battling Barnacles." The Detail Department (DetailEnjoyer), case file DD-705, last updated Mar 18, 2026. https://detailenjoyer.com/case/battling-barnacles/

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