To some extent I am a paper tiger (rawr!)
Most of my pre-licensure experience was on a 20ft salt flats boat that I used for work in FL for a solid year. Years later I bought a 34ft recreational trawler here in the Seattle area. Dry weight was about 20,000lbs, IIRC it was a documented as a 13ton vessel. To get myself a price break on insurance, I submitted a letter from my FL employer with some additional logged days for my 360 days experience and took the CG administered test. This was back when they still had actual CG examinations and it wasn't all contracted to schools. The Federal government saw fit to issue me a 50 ton inland license with a towing endorsement (the supplemental towing exam was the easiest bit). I have long since sold that trawler and downsized my boat to a 16ft rib. But I have taken required annual refreshers and drug tests to maintain my license. Could I hop on a tug to Ketchikan as a "master" and tow a barge up there? In theory yes, (the inside passage is "inland" waters ironically). I would be crazy to do it and nobody in their right mind would hire me for that position or even as a mate, not even as a deckhand (I don't have an AB).
I do think I am probably one of a handful of the more capable dive skippers in Puget Sound at this time. The really good guy left the business, one other skipper is roughly like me but has a more capable boat and a nearshore license. Another is trying to sell his boat. Another boat went out of business because it could no longer pass its inspection. The other diver operators are capable but don't know about the especially challenging sites to put divers on them. I don't operate commercially whatsoever, I don't even take gas money.