The locals call this area Gaidouronisia (donkey islands) and it’s a gathering of small islands just under 2 miles off the coast of Ouranoupolis and Ammouliani.
You may go there by renting a boat from Ouranoupolis or Kamboudi. (no license needed).
Another way of reaching the Drenia islands is by the kaiki boats which leave from the main harbour (in front of the Tower) of Ouranoupolis starting at 10:00 am and every hour until 18:00 pm daily.
There is a lovely tavern awaiting you!