That's how it works in the Netherlands. Kids get level A first, then B etc. They must pass the test at the end. Level A is basically normal above water swimming. B requires certain distances of under water swimming. Higher levels include swimming with full clothes on and swimming out from under a larger plastic thing with a hole they "fell through" to simulate typical water emergencies.
Swimming courses in the US only test swimming under normal conditions, in a pool with a swim suit. To get tested for ability in adverse conditions you need special courses which some orgs like the boy scouts offer.
What's really crazy is how easy the minimum requirements even for Red Cross lifeguard training are. When I did it, the "hardest" swimming qual was something like swimming 500 meters. That really should be table stakes for merely calling yourself a swimmer.
500m is 5 back and forth olympic pool. This is something.
I used to swim for my high school team. I learned to hate pools. Now I want to get back to vary the physical activity (thanks god for the headsets you can wear in the water)
500m is what I plan to ultimately do, for many people who "can swim" this is already a lot.
GP mentioned Red Cross lifeguard training which is specific to pools. They also have waterfront lifeguard training for lakes and rivers, but ocean lifeguards fighting significant currents go through a much harder certification done by other organizations like the United States Lifesaving Association.
It's much more strenuous and far fewer people make it through, thanks in part to the physical requirements.
There aren't any official universal tests that I know of. Different trainers might give a certificate, but most of it is very informal in the US. The standards are extremely low.
Organizations like BSA have different courses and tend to certify their members by different levels for what privileges they have in the water. The Red Cross and YMCA have the most recognized certifications, mostly for their lifeguard courses.
If you want a good idea of how much of a joke the standards are in the US, the basic test to be in the Navy is only a deep water jump, 50 yard swim, and 5 minutes prone float. Most other branches don't even have a swim test requirement.
That's how it works in the Netherlands. Kids get level A first, then B etc. They must pass the test at the end. Level A is basically normal above water swimming. B requires certain distances of under water swimming. Higher levels include swimming with full clothes on and swimming out from under a larger plastic thing with a hole they "fell through" to simulate typical water emergencies.