Conventional underwater cleaning is coming under environmental and regulatory pressure.
Surface compatibility, capture rates and coating condition.
Ports are taking an increasingly differentiated view of underwater cleaning.
A location-based approach: consider ports, coatings and cleaning objectives together.
In-Water Cleaning with Capture (IWCC) combines the mechanical removal of fouling with the collection of released material – biocide particles, organic fragments and living organisms – before it enters the surrounding water. The basic principle: a cleaning unit (brush cart, disc unit or water-jet platform) operates beneath a capture shroud connected via suction hoses to a filtration unit at the water surface or on board.
The critical technical parameter is the capture rate – the proportion of released material that is actually collected. Reputable systems achieve capture rates of 90-97 % for particles above 50 μm. For dissolved biocides (copper ions, zinc pyrithione), values are significantly lower – often 50-70 % – because dissolved substances pass through the filter. Some systems therefore employ additional chemical binding stages (activated carbon, ion exchangers), which increases operating costs.
Surface compatibility is the second critical factor. Rotating brushes with hard bristles are unsuitable for foul-release coatings – they destroy the smooth silicone surface. Soft cleaning discs or calibrated water jets are compatible but reach their limits with heavy calcareous fouling. This means: IWCC works best when deployed proactively – at light to moderate fouling levels where gentle methods suffice.
System size varies considerably. Compact units for diver-supported cleaning are suited to small areas (sea chests, propeller shaft, boot-topping area). Large-scale ROV-based systems can process entire hulls but require substantial infrastructure: support vessel, filtration plant, trained personnel. Costs typically range from USD 15,000-50,000 per operation – depending on vessel size and fouling level.
The practical significance of IWCC lies less in the technology itself than in the market access advantages it provides. Ports such as San Diego, Auckland and Sydney now only permit underwater cleaning with approved capture systems. Operators wishing to clean there must have the service provider and system pre-approved – a process that can take weeks.
For operators this means: the decision for or against IWCC is not purely technical but logistical. Which ports in the trading area require capture? Which service providers are approved there? What is the lead time for approval? This information must be part of voyage planning, not a reaction to problems en route.
A further practical aspect is documentation. IWCC operations generate a data set: before-and-after inspection, filtrate analysis, capture rate measurement. These data are immediately usable for the Biofouling Management Plan, CII evidence and port state compliance. Unlike conventional cleaning without capture, which often yields only a diver report, IWCC provides an audit-proof documentation chain.
The IWCC market is in transition from niche to mainstream. Leading providers such as ECOsubsea, HullWiper and Fleet Cleaner have expanded their presence over the past five years to more than 50 ports worldwide. The technology is available – but not everywhere. In parts of Africa, South-East Asia and South America, significant coverage gaps remain.
The IMO revision of the Biofouling Guidelines is expected to further accelerate demand. If capture becomes a prerequisite for lawful underwater cleaning – which is already the case in Australia and New Zealand – operators must factor IWCC availability into their route planning. This changes port selection and thus operational geography.
Before deciding on IWCC, operators should answer three compatibility questions: (1) Coating compatibility – Is the system deployed approved for the existing coating type (SPC, FRC, CDP)? The coating manufacturer should confirm in writing that the cleaning method does not affect the warranty. (2) Port compatibility – Is the chosen IWCC provider approved at the target port? Approval status changes; monthly updates are advisable. (3) Cost-effectiveness – At what fouling level does IWCC pay off compared to continued operation with increased consumption until the next docking?
The answers vary according to vessel type, trading area and coating condition. A blanket recommendation is not possible – but a structured assessment along these three axes provides a robust decision basis.
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