The nature of the Dead Sea is also worth describing. It is, as I have said already, bitter and unfruitful. It is so buoyant that it bears up the heaviest things that are thrown into it; nor is it easy for anyone to make things sink therein to the bottom, if he had a mind so to do. Accordingly, when Vespasian went to see it, he commanded that some who could not swim, should have their hands tied behind them, and be thrown into the deep, when it so happened that they all swam, as if a wind had forced them upwards. (Jwr 4:476-477 JOE)
That’s just how he rolled, I guess.