UWILD Survey Singapore — Class-Witnessed Underwater Inspection in Lieu of Drydocking

What Is a UWILD Survey?

UWILD stands for Underwater Inspection in Lieu of Drydocking — a class-witnessed underwater survey that satisfies a vessel's docking-survey requirement without ever lifting the ship out of the water. Classification rules require the underwater parts of a hull to be examined at fixed intervals, and traditionally that examination is done with the vessel high and dry in a graving dock or on a slipway. A UWILD achieves the same regulatory outcome differently: the ship stays afloat, a survey crew examines every underwater item in the water, and the vessel's classification surveyor witnesses the inspection so that it is accepted in lieu of the drydock survey.

For a vessel operating in and out of Singapore — the world's busiest transshipment and bunkering hub — the appeal is immediate. Drydock slots are scarce and expensive, and every day a ship spends out of the water is a day it earns no freight. A UWILD lets an eligible vessel discharge its survey obligation at anchorage or alongside, and sail on schedule. It is the flagship service in our marine and underwater inspection range for exactly that reason.

Crucially, a UWILD is not a lighter or informal check. It examines the same items a drydock docking survey would cover, to the same standard, and it is scoped, attended and signed off by class. The only thing that changes is that the work happens underwater rather than in dock.

Why Operators Choose UWILD Over Drydocking

The commercial case is the headline. A drydocking is one of the largest planned costs in a ship's operating life — the dock booking itself, tugs and pilotage to reach the yard, staging, cleaning and the days or weeks the vessel spends out of revenue service all stack up. A UWILD removes the largest of those items. There is no dock hire and no positioning voyage to an empty yard slot; the survey is carried out where the ship already is, and the vessel remains available for its next fixture.

Downtime is the second driver. Taking a ship out of service to drydock can idle it for a week or more even before any repair work begins. A UWILD is typically completed in a single working window while cargo, bunkering or lay-up carries on around it, so the survey stops being a scheduling bottleneck. For owners managing a tight docking window against a class deadline, that flexibility is often decisive.

A UWILD also gives early, evidence-based intelligence on hull condition. The high-definition video record and thickness readings produced during the survey feed directly into maintenance and repair planning, so that when the vessel does eventually drydock, the yard scope is known in advance rather than discovered on the blocks. In practice, a UWILD both defers cost and de-risks the drydocking that follows.

What a UWILD Survey Inspects

A UWILD covers the entire underwater portion of the vessel — the same items an attending surveyor would examine on the blocks. Every finding is video-recorded, referenced to a hull location and, where required, backed by measurement.

How a Class-Witnessed UWILD Is Carried Out

The defining feature of a UWILD is that it is witnessed by class in real time. We deploy a survey crew using a work-class ROV and, where access demands it, commercial divers, both equipped with high-definition cameras and dedicated lighting. As the crew works methodically around the hull, the live video feed is displayed to the attending classification surveyor, who directs the survey from the topside station — calling the crew to specific frames, requesting closer views of a suspect area, and nominating points for ultrasonic thickness readings. Because the surveyor sees and confirms each item as it happens, the survey carries the same evidential weight as a physical drydock examination.

A UWILD follows a systematic path so nothing is missed: the flat bottom, bilge keels and turn of the bilge; the sea chests and their gratings; the rudder, propeller and stern gear; the thruster tunnels; and every hull penetration, anode and marked reference point. Divers and ROV pilots record continuous positional video, and thickness gauging is performed underwater at the locations the class rules and the attending surveyor require.

Where marine growth obscures the steel, the hull must be cleaned before the surveyor can assess coating and plating condition — which is why UWILD is frequently paired with underwater hull cleaning. The advantages of the in-water approach are clear:

• Vessel stays in service — no dry-dock booking, positioning voyage or lost revenue days while the survey is completed.
• Complete, witnessed record — continuous HD video of every item, viewed and accepted live by the classification surveyor.
• Objective measurement — ultrasonic thickness gauging and clearance checks give class hard data, not just imagery.
• Diver safety and access — ROV handles low-visibility and confined niches, with divers deployed only where hands-on work is needed.

Class Rules & Vessel Eligibility

UWILD is governed by the classification societies and the framework set out by the International Association of Classification Societies (IACS). The major societies — ABS, DNV, Lloyd's Register, Bureau Veritas and ClassNK — each publish rules setting out when an underwater inspection may be accepted in lieu of drydocking, the items to be examined and the qualifications required of the survey firm and its divers. IACS unified requirements and IMO survey guidelines sit above these, and diving work itself follows recognised safe-practice standards such as the IMCA diving guidance.

Eligibility is set by the vessel's own society and is never automatic. A ship generally needs the in-water survey class notation and must meet the age and condition criteria in the rules — for many vessel types a UWILD is accepted at an intermediate docking survey but not at every special survey, and vessels with poor coating history or advanced corrosion may be required to drydock. The attending surveyor and the society hold the final decision, so eligibility should be confirmed with class before the survey is scoped. We do not hold ourselves out as an approved supplier of any particular society; we deliver the survey to the rule framework and coordinate with your appointed surveyor and society so the inspection is accepted.

Where a UWILD Fits in Your Survey Programme

A UWILD rarely stands alone — it sits within a wider in-water inspection and maintenance programme, and the surrounding services are what make it efficient.

Why Choose SG Drone Inspections for UWILD

We are a specialist marine and underwater inspection provider working across Singapore's port, anchorages and shipyards, delivering surveys that classification surveyors accept.

Frequently Asked Questions