"Swimpruf" designation on new Sub?

Forgive me for my ignorance here. I don't, and never have, owned a Rolex. But I've been keeping my eye out for a good deal on a new model (114060) Sub and came across a listing which included the following pic. Watch is from 2016 and looks proper, but I've never seen (or noticed) the "Swimpruf" designation before. A bit of Googlling seems to suggest that it was used for a while on watches maybe 20 years ago. So what's the deal? Is it normal? Thanks for educating me..

Yes that is the normal green tag for the new 6 digit Sub.

Ah OK, thanks. Wasn't sure. 👍

Minimum of 300 meters and they call it “swimm proof”. Now that is a statement !!!!