Underwater Inspection and UWILD Providers

Two different jobs share this name. One is an owner's inspection: a diver goes down because something is suspected - a vibration, a fuel figure that has drifted, a bump alongside - and comes back with video and an opinion. The other is a class survey conducted in the water instead of in a dock, on a scope the society agreed beforehand, producing a record that satisfies a statutory requirement. The first can be booked in an afternoon; the words underwater inspection cover both, which is why quotations for the two arrive looking similar and priced nothing alike. The second decides whether a ship spends a week in a yard, and everything about how it is arranged follows from that.

What an Underwater Inspection of a Ship Covers

A standard underwater hull inspection works the vessel from bow to stern: shell plating and welds, the boot top and flat bottom, bilge keels, the bulbous bow, sea chests and their gratings, thruster tunnels, the rudder with its pintles and stock, and the propeller with its boss and rope guard. Anode condition and coating condition are recorded throughout, because both tell the surveyor how the hull has been looked after between dockings.

An underwater ship inspection is only as good as its visibility, and that is a practical constraint rather than a formality. A hull under an inch of weed cannot be inspected at all, which is why survey work is often preceded by hull cleaning - either the whole hull, or spot cleaning of the areas the scope names. A contractor who quotes a survey without asking about fouling condition has not thought about whether the survey can actually happen.

UWILD: Underwater Inspection in Lieu of Drydocking

UWILD is the reason most of this work is booked. Under SOLAS Chapter I Regulation 10, cargo ships undergo two inspections of the outside of the bottom within any five-year period, with the interval between them not exceeding 36 months. Traditionally both meant a dock. An in-water survey lets one of them be carried out afloat, and on qualifying tonnage this converts a docking into a port call.

The governing document is IACS Unified Requirement Z7.2, which sets out what an in-water survey in lieu of drydocking has to demonstrate and under what conditions a society may credit it. The commercial arithmetic is straightforward: a UWILD inspection costs a fraction of a docking and, more importantly, none of the off-hire days, the passage to the yard, or the slot booked months in advance. That is why the enquiry usually arrives with a survey window already fixed and a rotation that will not bend.

UWILD Requirements: When Class Will Accept an In-Water Survey

Not every ship qualifies, and the conditions are cumulative rather than alternative. The vessel normally carries an IWS notation on its class certificate, which implies design features the survey depends on - hull markings that let a diver report position, and rudder and tailshaft arrangements that can be examined afloat. Underwater visibility at the site has to be adequate and is judged on the day, not promised in advance. The hull has to be clean enough for the plating to be seen. The contractor has to be recognised by the attending society, and the survey scope has to be agreed before anyone enters the water.

Age is the condition owners most often overlook. Societies commonly restrict in-water survey in lieu of drydocking on older tonnage, and the thresholds and ship-type exceptions differ between them. Checking the vessel's specific position with its own society, rather than assuming an industry rule, is the first step in any UWILD requirements discussion.

The UWILD Procedure, Step by Step

A UWILD procedure begins on paper. The scope is agreed with the society - which areas, how many thickness readings if any, which welds, what constitutes an acceptable finding - and the contractor's method statement is accepted. Only then is the attendance scheduled.

In the water, the diver or vehicle works to a numbered grid keyed to the hull markings, so every image can be located afterwards. Video runs continuously with commentary and a position readout, and most societies now accept a live feed to a surveyor ashore rather than requiring attendance on the quay. Thickness readings, where the scope calls for them, are taken by a qualified diver-inspector and belong with underwater NDT rather than with the visual team. The uwild survey closes with a report in the society's format, and the credit is granted against that document, not against the dive. Anything found outside the agreed scope is recorded but does not extend it; extending a scope mid-dive without the surveyor's agreement produces findings nobody has to accept.

What the Classification Societies Require

Each IACS member - ABS, DNV, Lloyd's Register, Bureau Veritas, ClassNK, RINA, KR, CCS, IRS, PRS, CRS, TL - maintains its own in-water survey rules aligned to UR Z7.2, and the differences are in the detail rather than the principle: acceptable visibility, how the diver reports position, whether a live video link substitutes for attendance, and how thickness measurement is handled. Non-IACS bodies such as HRS, INSB Class, RMRS and TASNEEF publish equivalents for the flags they serve, and a vessel changing class mid-cycle can find the survey it planned is scoped differently by the incoming society.

What matters commercially is that approval attaches to the firm, not the diver. Under the IACS framework for service suppliers, a contractor is approved for a defined scope by a named society, and it is that approval which decides whether the report is accepted. The part of that same structure sitting above the waterline is surveyed through hull and structure providers, and on a renewal survey the two records are read together.

Diver Survey Against ROV Survey

A remotely operated vehicle covers a hull faster than a swimmer, carries better lighting and camera stabilisation than a helmet rig, and works where diving is restricted by depth, current, traffic or port rule. For visual coverage of open plating it is now the default on many attendances, and several societies accept ROV footage for the visual element of an in-water survey.

Divers keep the work that needs hands and judgement. Sea chests behind gratings, confined niche areas, anything requiring contact - thickness probes, cleaning a patch to see what is under it, measuring a dent - and any situation where the useful output is a professional opinion rather than footage. Most real UWILD attendances use both, and a contractor offering only one should be asked how the other half of the scope will be covered. Cost follows the same split rather than the technology: a vehicle is cheaper per square metre of open plating and more expensive per confined-area finding, so a scope written around the wrong platform costs more than the right one either way.

Damage Assessment After Grounding or Contact

The other half of this market is unplanned. After a grounding, a contact alongside, ice, or a suspected wire strike, the first attendance establishes what happened: extent, position, depth of indentation, whether plating is set in or torn, whether the propeller and rudder are affected. This kind of underwater inspection is not a class survey and should not be scoped as one - it is evidence, and it feeds three decisions at once: whether the vessel can sail, what the class society will require, and what the underwriters are told.

Where the finding calls for work rather than monitoring, the same team often continues into underwater welding and cutting, and where it does not, the report is what lets a yard quote before the ship arrives. A contractor who can move from assessment to repair without a second mobilisation saves days on an already unplanned event. Photographs taken by the crew from the deck are worth sending with the enquiry: they rarely show the damage itself, but they establish the time and the circumstances, which the underwriters will ask about.

Reading a Report a Surveyor Will Accept

The deliverable is the product, and it is worth specifying before the attendance rather than judging afterwards. A report that satisfies a society carries continuous video with commentary and diver or vehicle position, still images keyed to a numbered hull grid, before-and-after coverage where anything was cleaned, coating condition by area, anode condition with wastage estimated, measurements of any defect found, and the calibration record for any instrument used.

What separates a usable record from a folder of footage is that every frame can be located. An underwater inspection of ships that produces two hours of video with no grid reference is worth very little at the next survey, because nobody can say where the coating was sound and where it was not. Anode condition deserves a line of its own, because it is the part owners most often skim. Wastage patterns across the hull say more about the cathodic protection system than any single reading, and where the survey raises questions the follow-up belongs with cathodic protection inspection rather than with the next visual survey.

Choosing an Underwater Inspection Company

• Society approval held by the firm itself, listed society by society with the scope each one covers and the date it expires.
• Documented UWILD attendances on comparable tonnage, with a sample report available on request.
• Diver-inspector qualifications appropriate to the scope, and separate commercial diving competence under ADCI, IMCA or OSHA rules according to the region.
• Both diver and ROV capability, or a clear statement of how the other half of the scope is covered.
• Whether hull cleaning or spot cleaning for visibility is included in the price or quoted separately.
• Whether thickness measurement is in scope and who is qualified to take it.
• Deliverable agreed in writing before the dive - what video, what stills, what measurements - and how many working days until it lands.
• Presence in the ports where the survey window actually falls, since a survey deferred for lack of a contractor becomes a docking.

Where the vessel does not qualify or the finding is beyond in-water work, the alternative is a yard, and ship repair facilities quote against the same report the diving team produced.

Underwater Inspection Companies by Country

Underwater inspection services are tied to a place and a date at once: the window is fixed by the survey cycle, and the vessel is where the trade puts it. That combination, rather than price, is usually what decides the contractor. Ports with sheltered water and reliable visibility are worth planning the window around, because a survey abandoned for turbidity still costs the mobilisation.

• Underwater Inspection Companies in China
• Underwater Inspection Companies in the Philippines
• Underwater Inspection Companies in Ghana
• Underwater Inspection Companies in Mauritius
• Underwater Inspection Companies in Jamaica
• Underwater Inspection Companies in Gibraltar

Frequently Asked Questions

What is UWILD inspection?

Underwater inspection in lieu of drydocking: a class survey of the ship's bottom carried out afloat instead of in a dock, on a scope agreed in advance with the classification society. Where the society credits it, the survey satisfies a statutory bottom inspection without the vessel leaving service.

What are the UWILD requirements?

Typically an IWS notation on the class certificate, adequate underwater visibility on the day, a hull clean enough for the plating to be seen, a contractor approved by the attending society, and a scope agreed before the attendance. Societies also restrict in-water survey on older tonnage, with thresholds that differ between them.

How often is a bottom survey required?

SOLAS Chapter I Regulation 10 requires two inspections of the outside of the ship's bottom in any five-year period, with no more than 36 months between them. An in-water survey can replace one of the two on qualifying vessels; the other is normally still a docking.

Can an ROV carry out the whole survey?

For the visual element on open plating, often yes, and several societies accept vehicle footage. Sea chests, confined areas and anything needing contact or judgement still go to a diver. Most real attendances use both.

What does the UWILD procedure involve?

Scope agreed with the society, method statement accepted, then a dive worked to a numbered grid keyed to the hull markings, with continuous video, commentary and position. Many societies now accept a live feed to a surveyor ashore. The credit is granted against the report, not the dive.

Who pays for cleaning the hull before the survey?

Enough of it to see the plating. Sometimes that means the whole hull, sometimes spot cleaning of the areas in scope. Establish who is paying for it before the attendance, because it is the most common cause of a survey being extended or abandoned.