That is because you already knew that the shore of the Dead Sea is the lowest point on dry land. If a reader has to already know the information being conveyed in order to understand a sentence then the author has done a really crappy job.
No, its because when you link the "10 lowest places on earth", and everyone of them is deep under the ocean, its disingenuous to claim you have no idea what was meant when the Dead Sea was referenced as being the lowest point on earth. It doesn't take a genius to figure out the author was obviously referring to dry land, not ocean depths.