Going to Crete, Santorini and Naxos in September and planning on swimming and walking on the beaches...are beach shoes (aka aquasocks) recommended to cope with pebbles, sea urchins, etc.?

Yes.

Bring them along.

Another yes.

yes yes yes !!!!!

Not on every beach of course -- most on Naxos are sandy -- but you may come across the beach of your dreams, and see it has pebbles and stones for the first few feet ... and you want to be able to run right in...

Never use them but that doesn't mean I don't occasionally wish I did.
Lots of beaches have stones or pebbles - you learn to walk on them.

Definetely yes. Sands get pretty hot to step on with barefoot

Yes. I use them all the time. Make sure they're tight enough to stay on your feet when you swim. Mine are a bit too big and they feel as if they're going to come off as I'm swimming. But they save the feet from walking on all those pebbles. Seems like the only ones that aren't affected by the stones are small children.