UWILD surveys: what they cover, and when an ROV can do one

Underwater Inspection in Lieu of Drydocking is one of the few places in class compliance where the alternative method is genuinely cheaper, faster and safer than the original. It is also one of the most commonly misunderstood, because "an ROV can do it" is true in general and wrong in enough specific cases to matter.

What UWILD actually is

Statutory and class regulations require two bottom surveys in any five-year period, to confirm the integrity and watertightness of the hull. Traditionally at least one of those meant taking the vessel out of the water. UWILD is the mechanism that lets an in-water inspection substitute for the docking, under defined conditions.

The point is not that inspection becomes optional. It is that the docking becomes optional, and the docking is where nearly all the cost and nearly all the off-hire sits.

What the survey has to show

This is the part worth being precise about, because it determines the equipment specification more than anything else. The footage has to clearly show:

• The hull markings - draft marks and identification
• All sea chests, inlets and discharges
• The rudder and pintles
• The propeller

The four things the footage has to show

Where corrosion or damage is found, the surveyor will want it examined further, and may call for thickness testing. Thickness measurement is not required on every UWILD - it is a consequence of what the visual inspection turns up. That distinction matters when specifying, because it decides whether you need a measurement payload or only a camera.

When class will accept an ROV

Most IACS class societies accept ROV-led in-water surveys, provided the vehicle delivers high-definition live video and has cleaning capability so that fouled areas can be revealed rather than photographed through weed. The live element is important: the surveyor typically needs to direct the inspection as it happens, not review a recording afterwards.

Two caveats that catch people out:

• Acceptance is per society and per vessel. Requirements vary between class societies and with the vessel's age, type and history. Confirm the specific requirement with your own surveyor before you plan the programme around it.
• Some ports still want standby divers. Local rules, not class rules, and they apply to particular hull or sea chest tasks. Check the port as well as the society.

How long it takes

A standard in-water survey on a commercial vessel usually runs somewhere between six and twelve hours. That is a working day, alongside or at anchor, against a docking measured in days - which is the whole economic argument in one sentence.

The variable is rarely the vehicle. It is fouling, visibility and how organised the inspection plan is. A survey that has to stop while someone works out which sea chest is which takes considerably longer than one with a marked-up plan.

Doing it yourself, or contracting it

Both models work, and the right answer depends on how often you need it.

• Contracted survey suits a single vessel with a five-year cycle. You are buying an outcome and a report, not equipment.
• In-house capability starts to pay when a fleet generates several surveys a year, or when the same vehicle also does routine checks between them - propeller condition, biofouling assessment, anode wear.

The second case is usually the stronger one, because the equipment stops being a compliance cost and becomes a condition-monitoring tool. A vehicle bought for UWILD that then does monthly propeller and anode checks pays for itself on fuel long before the next survey.

Specifying the vehicle

For UWILD work specifically, the questions in order of how much they change the answer:

• Water clarity where you normally lie. If visibility is routinely poor, camera specification alone will not carry the survey and you should be looking at acoustics as well.
• Who operates it. Modern inspection-class vehicles are designed for a non-specialist single operator, which is what makes crew-run inspection realistic.
• Whether you need to clean. Revealing a fouled sea chest is a requirement, not a nice-to-have.
• Whether thickness measurement is likely. If the hull has history, specify for it now rather than discovering it mid-survey.
• Depth. Last, deliberately. Hull work is shallow; most inspection-class vehicles have far more depth rating than a UWILD needs.