You can visit this island, either by hiring a boat (relatively expensive) from Makrigialos, or by your own. The nearest harbour to moor your own boat would be at Atherinolakkos.
If you were intending to visit, remember that both staying overnight and camping on it are prohibited.
The beaches of Koufonisi (all 36 of them!) are, however, quite wonderful – the blue-green crystal-clear water, the white rocks and cliffs and sand-dunes, and fine white beach-sand .. all lend it a ‘tropical’ feel.
Remains of a Roman settlement remain.
Koufonisi has no trees, nor any organization – be sure to take whatever you need for your visit with you!