Because if you've played the beta you'd realize they've added a "stage death" to Sandover Village to prevent people from camping there to avoid supers.
In the old beta build, it was actually being at the bottom half of the stage and not just the water. Not sure what the timing is for the final build but this is a stage death that affects every character.
I have the Beta. There was no stage death in Sandover Village
It's not instant. Stay in the water for about 5 seconds or so. You get transported back on the green hill, stunned, with less AP.
THIS IS ACE