The locals call it "Gaidouronisia" and it is a small island complex two miles from Ouranoupoli and Ammouliani.
You can go with your own boat or hire a boat from Ouranoupoli or Kaboudi (no diploma).
It has taverns for food and recreation.
View the embedded image gallery online at:
https://ouranoupolis-akrogiali.gr/en/ouranoupoli/drenia-islands#sigProId16aff4b8d7
https://ouranoupolis-akrogiali.gr/en/ouranoupoli/drenia-islands#sigProId16aff4b8d7