As a child, I used to spend summer with family in Agami, west of Alexandria. The blue water of the Mediterranean, and the white sand were a major part of the activities there.
Several years ago, my two eldest daughters were subjected to the same torture. We were watching a Balans بلنص (traditional fishing boat in Alexandria) hauling in its catch to the shore, as often is the case. As the net was taken out of the water, the girls ran between the net and the surf. The net was dripping a lot of water, and since there were lots of jellyfish in it, the water was like a caustic fire. That resulted in a lot of crying and tears.
In the Red Sea
When snorkeling in the Red Sea, I was often stung by the fire coral, but did not suffer much from jellyfish. The most common species was the upside down jellyfish (Cassiopea), which lived in colonies on the sand, having their tentacles up, and its umbrella down to the bottom.
As the BBC reports, there is an ongoing infestation of jellyfish in the Mediterranean in summer of 2006.