I was thinking about that when I was dropping my 6 year old off at some hobbies earlier - it’s pretty much expected to have learned how to ride a bicycle before starting school, and it massively expands the area you can go to by yourself. When she went to school by bicycle she can easily make a detour via a shop to spend some pocket money before coming home, while by foot that’d be rather time consuming.
Quite a lot of friends from outside of Europe either can’t ride a bicycle, or were learning it as adult after moving here, though.
edit: the high number of replies mentioning “swimming” made me realize that I had that filed as a basic skill pretty much everybody has - probably due to swimming lessons being a mandatory part of school education here.
He must be referring to riptides. In some spots the water hits the beach as waves. In others nearby, the water gets pulled back into the ocean, and those are the spots you need to avoid.
Then depending on the ebb and flow of the twice-daily tides, the riptides are stronger or weaker.
There are ways to see where the riptides are, yet many people from my own coastal town are oblivious to these dangers. Inland/landlocked tourists are even more oblivious and vulnerable.