Additional to this, bullets won't penetrate these windows. I was trying to shoot at a enemy through such window, but bullets were not hitting him at all. Window made breaking glass sound, but did not break. This was a small one floor building in Agia Marina.

In the scuba mission after I sabotaged the boat, 2 divers jumbed in to the water and started shooting at me. I killed the first one, but could not kill the second one. He started swimming to shore right past me, and I emptied clip and a half to him. Hits were making a small cloud of blood on each hit, and he swam past me very close, so he should have died. He just kept swimming and disappeared in to the darkness.

Later on in the mission when I was already out of the water, I noticed one of the enemies I had killed was wearing scuba gear, so it must have been him.