I've seen the same sort of thing happen in a baptismal pool in Waco, TX about 7 years ago. In that case the baptismal pool was fiberglass with PVC plumbing so there was no natural ground path from the water to the earth. There was a pin-hole leak in the immersion electric heater that warmed the recirculating water (same thing as in electric hot water heaters). That electrified the water to around 90 volts, which had probably been charged for weeks or months until the second part of the accident occurred. That's when the preacher couldn't be heard by the congregation, and somebody handed him a hard-wired microphone that was, in fact, properly grounded. That completed the current path from his body in waist-deep chlorinated water through his chest to his wet hand through the metal body of the microphone. The body of all microphones are bonded to the shield of the XLR cable, which in turn is bonded to the mixing console, then bonded to the ground contact of sound system's power cord. There was no GFCI feeding that recirculation pump or heater, which would have protected the preacher by tripping before electrocution.
Since then I've taught in my HOW-TO and NoShockZone seminars that churches should do occasional tests of their baptismal pools, microphones, and guitars/keyboards for an electrification by using a non-contact tester. I've even given away dozens of Fluke VoltAlerts to my attendees after showing how to test safely and telling them to call an electrician immediately if they find anything that makes a NCVT beep on stage.
I think that any pool or water feature that has AC power running pumps, lights, or heaters, should require a periodic inspection for voltage potential above earth ground. Extech even makes the DV-50, a non-contact tester on a telescoping wand used for checking manhole covers for electrification. That would certainly have identified the charged condition of the baptismal pool in Waco as well as this latest tragic situation in Kissimmee. And, or course, these water features and outside displays that are connected to 120 volts AC should be properly bonded/grounded and protected by a GFCI breaker.
