Yeah, this is basically how it goes. It depends what country you grew up in. Canada is the same way, almost everyone who grew up in Canada can swim (not necessarily well, but able to manage). This is partly due to the number of lakes that exist near populated areas so swimming is a common passtime and boating accidents are a fairly high cause of accidental death. There are some countries where it is much more rare.
Firefox on iPhone isn’t Firefox in the way that matters here. All iOS browsers are forced to use Safari’s rendering engine. iOS alternate browsers are just different UI and things like bookmark management on top of Safari.