I cannot maintain my balance at the beach, standing in the surf,
and the bottom stones & shells hurt my feet - even wearing reef-runners, so I seldom go on the beach when I go to the ocean with my family.
Pools are where I prefer to swim (and still have to wear reef-runners cause the rough bottoms hurt me too).
Aside from sand, pebbles/crushed gravel (roads & driveways) is difficult for me to walk on.
Cobblestones (I live in the 'historic' section of town)
are very difficult to walk on.