Hull integrity testing is a regulatory requirement for all US Coast Guard certified vessels. I conducted these tests and took ultrasonic thickness measurements (UTM) on three separate occasions while at Delaware Bay Shipbuilding, working under contract with a licensed naval architect who coordinated the inspection work.
The vessels included two US Coast Guard cutters dry docked for scheduled servicing and a cruise ship in New York Harbor.
The process involved following a systematic grid pattern across the hull, focusing on low points between bulkheads and structural support beams where salt water is most likely to pool and accelerate corrosion through pitting. On the cruise ship I worked from inside the vessel, testing sections of hull plating that were exposed to high movement salt water and showed visible signs of wear, mapping thickness readings across a grid with additional attention and measurement to areas of visibile concern.
Readings were documented and reported to the naval architect, who used them to produce the formal compliance reports submitted to the relevant authorities.
It was methodical, detail oriented work with real consequences if done carelessly. Working on vessels of that scale, a Coast Guard cutter and a commercial cruise ship, early in my engineering career gave me an appreciation for what it means to sign off on something that people's safety depends on.