The UWILD Loophole: Why ROV Surveys Cut Your Required Exams in Half
By Nadia Fournier, Marine surveyor and insurance adjuster. Reviewed by Amanda McCallister, editor.
Ship Husbandry & In-Water Repair | Underwater Inspection Last month on San Francisco Bay, I watched a Saab Seaeye Falcon descend through twelve feet of clear water off the stern of a 180-foot passenger ferry. The port engineer had pulled the boat from service for one morning, not one week, because we were doing the underwater survey with an ROV. The dive supervisor wasn't even on the dock. Thirty minutes later, we had a recorded pass of the propeller, the rudder, the sea chests, and the hull anodes, and the ferry was back to work by lunch. That's the reality I face as a marine surveyor and insurance adjuster. The UWILD rule—underwater inspection in lieu of drydocking—lets a vessel owner skip a required haulout, provided the survey is approved and gives the same confidence as a drydocking. An ROV can do that. In many cases, it can do it faster and cheaper than a diver. And because the typical five-year cycle requires two credited examinations with a maximum interval between them, replacing one of those exams with an ROV survey means you've cut your required out-of-water examinations in half—give or take a shifting schedule.
The UWILD Rule, Minus the Hype
Let's get specific. For passenger vessels under 46 CFR Subchapter H, 71.50-3 sets the underwater examination requirement, and 71.50-5 allows the Coast Guard to approve an underwater survey in lieu of drydocking. That approval isn't a rubber stamp. You'll submit a survey plan detailing the ROV's capabilities, the areas to be covered, the positioning method, and the recording format. If the vessel has a history of hull damage or the water is murky, the approval will include conditions. The schedule generally works out to two credited examinations within a five-year period, with a stated maximum interval between them. In practice, that means most operators book one drydocking and one UWILD per cycle. The UWILD substitutes for the second out-of-water exam. That's where the number halves.
Diver vs. ROV: What You Actually Get
Divers are flexible. They can clean the hull, feel for cracks, and use a UT gauge directly on the steel. They can also adapt on the spot. But a diver survey comes with overhead: a team of at least two to four people, surface support, decompression planning, and a weather/current window. I've seen a 10-knot tide scrap an entire day's work. A diver in a contaminated harbor also has more exposure risk, not just from current but from pollution. An ROV keeps people out of that water. An ROV is a smaller footprint. A two-person crew can deploy a VideoRay Defender or a Deep Trekker with a 4K camera, LED array, sonar, and a cathodic potential probe. You watch live video from the dock. In clear water, I've completed a full hull survey in under an hour. The limitation is tactile. An ROV can't clean heavy fouling, and in zero visibility you're flying blind without sonar. So it's not about one being better in every case. It's about what the job needs. For a routine clean hull in clear water, an ROV is enough. For damage assessment or heavy growth, call in a diver.
Why That Halves Your Required Exams
Consider the schedule. If your vessel needs two out-of-water exams in five years, you used to book two drydockings. Each one costs dock fees, cleaning, painting, and days off hire. The UWILD rule lets you swap one of those for an in-water survey. Now you have one drydock and one UWILD—that's the halving. An ROV makes the substitution practical. A dive team for a UWILD might charge a day rate plus three to four divers and a separate boat. An ROV survey can be done by two people in a few hours, with the vessel alongside the dock. That reduces cost and scheduling friction—call it a practical advantage. You can run the ROV survey during a brief turnaround, not a week-long yard period. So you're more likely to stick to the schedule and take advantage of the rule. And because the ROV is less disruptive, you're less likely to postpone the exam, which is how surveys get missed. On the insurance side, a well-documented ROV video is better than a few pages of diver notes. You get a continuous record. That's evidence, and in a claim dispute, evidence is everything. The insurance file is made of data, not anecdotes. That's not an argument against divers—it's an argument for capturing the data.
Caveats and a Digression
Not every vessel qualifies, and not every ROV will pass review. The approval depends on the vessel's age, history, and the surveyor's judgment. If visibility is under a few feet, sonar becomes necessary, and sonar can miss fine cracks. Complicated stern appendages or bow thrusters may require a diver's eyes. And an ROV can't do repairs. It can't clean a sea chest. It can't weld a steering knuckle. Here's a digression from a survey I did near Mobile. The ROV tether kept fouling on a current around the sea chest, so we sent a diver down to free it and do a quick feel of the limber holes. Ten minutes of diver work, an hour of ROV footage, and we had the answer. That's how it works in the real world—the ROV gives you efficiency, but the diver gives you depth. You might use both. The bottom line is that the UWILD loophole is real, and ROVs are the reason it's worth using. If you're sitting on a vessel with two haulouts per five-year cycle, you have a way to cut that in half. It's not a cheat. It's a rule that rewards good planning and modern tools.
Frequently Asked Questions
Is an ROV survey as good as a diver survey for UWILD? It depends on the goal. For a routine hull and propeller exam in clear water, an ROV with HD cameras and a UT gauge is often sufficient. For close-up work in zero visibility or if you need to clean the hull, a diver is still the better choice. Can an ROV replace drydocking altogether? No. The regulations require a certain number of credited examinations, and only a limited number can be in-water surveys. You're substituting, not eliminating. Typical cycles still include at least one drydocking. How much does an ROV UWILD cost compared to a diver? It varies. A dive team typically charges a day rate per person plus support and boat costs. An ROV package often has a mobilization fee and a daily rate. The real saving is time and crew size, but the total depends on the vessel and location. Who approves the ROV plan for a UWILD? For passenger vessels under USCG regulations, the Coast Guard approves the plan. If the vessel is classed, the class society does. The plan must specify the ROV's sensor suite, positioning, and data recording methodology before the survey.