Armenaki is a very small beach located between Armeni and Ammoudi, below Oia village in the caldera bay.
There are no beach facilities, shops or restaurants there, but it is a very quiet place where you can swim in crystal clear deep waters.
It is accessible by boat, or if you are in a good shape, you can climb down the cliff by taking the downhill street from Monastiri area in Oia village that leads to Armenaki.