they are called streams and they are not that deep.
to enter the Med sea you have to low your sails inside the water for ~4 meters
to exit the Med sea you have to low your sails inside water for ~15 meters

Allah Almighty makes the parable of deeds of atheists and disbelievers as a man who lives in the deep of the sea where he is covered by a layer of deep waves that is covered by a layer of surface waves which is covered by darkness

STOP INSULTING CTHULHU !