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.
Sand. It’s coarse and rough and it gets everywhere, but that shouldn’t stop you from learning to swim, it can be made easy. Start by practicing floating and familiarizing yourself with the medium. Being at ease is essential, so stay wherever the waterline reaches your shoulders. Breathing is an important part of the ordeal, because full lungs keep you afloat. Breaststroke and sidestroke are good starting points, whichever resonates more with you. Personally I think sidestroke is better because it’s very smooth and the body falls quite naturally into this position (look it up on youtube for tutorials, it’s very simple). Last but not least, we learn by playing, so have fun. 😀