Can fouling be removed without damaging the underwater hull?

This is one of the questions most frequently asked by clients who engage Safinah to give an expert opinion on fouling type(s), fouling severity, cleaning methods, cleaning damage and effect on performance.

It is asked by ship owners, marine legal firms and marine insurance firms, including P&I clubs.

For a general answer to this question, read on…

What is the difference between the barnacle fouling in photograph 1 and photograph 2? 

Imature Barnacles

Photograph 1

Mature Barnacles

Photograph 2


Photo 1

  1. These barnacles are relatively immature (around 1 month old).
  2. The barnacle ‘feet’ will not have penetrated into the coating.
  3. These barnacles can be removed by underwater cleaning, if carried out correctly, without damaging the hull coatings or leaving broken barnacle bases.


Photo 2

  1. These barnacles are relatively mature (over 3 months old).
  2. The barnacle ‘feet’ will most likely have grown into the hull coatings.
  3. These barnacles cannot be removed by underwater cleaning without causing some damage to the coating such as:
    • Brush marks removing the antifouling coating due to the increased force required
    • Broken barnacle bases remaining on the coating
      This level of barnacle fouling would require the hull coating to be removed along with the whole barnacle shells.
Do not leave barnacles to mature.  they become impossible to remove by underwater cleaning. Vessel movement will not remove barnacles, even those shown in photograph 1.

Safinah Group are recognised experts in coatings and corrosion claims, arbitration and dispute resolution. We provide independent, impartial advice to insurance companies, law firms, loss adjusters and P&I clubs worldwide.

For no obligation advice on any aspect of coatings or corrosion, contact our insurance and litigation experts on +44 1670 519 900 or email the team at

Alan Walker, Market Sector Manager: Marine (Marine Team, Insurance Team)The Author
Alan Walker