This was a powerful combo when Ravnica and Time Spiral was in Type2. Now it is not that strong, but still usable in EDH. To form the combo, we need to play Brine Elemental first.
Don’t worry about morph it and then turn it face up or just cast it, we just need it on battlefield. The key is we morph Vesuvan Shapeshifter and then turn it face up to copy Brine Elemental. According to the rule, when Vesuvan Shapeshifter’s triggered ability of copy resolves, it is still in the state turning face up. So it will trigger the triggered ability copied from Birne Elemental, that is “each opponent skips his or her next untap step”. Thus your opponents will skip their next untap step, and always they will pass their turn and it comes to your turn. In your upkeep of this turn, turn Vesuvan Shapeshifter face down and turn it face up to copy Brine Elemental again. Your opponents will skip their next again. You already notice this process will be infinite, your opponents will never get their permanents untapped. It is the combo.
In my opinion, it is not a very good combo, because your opponents can still play lands and these lands is not tapped. So they can still have a chance to kill one of Brine Elemental or Vesuvan Shapeshifter. Anyway, it can control your opponents for a long time.
