Holy moly. That's quite impressive!
I'm no electrical engineer, but I was always under the impression that it took a SIGNIFICANT amount of power to electrify a large body of water. Like, even your house mains wouldn't cause a problem directly into a swimming pool - although I think it does depend a bit on the type of fault (open end, short, AD-DC, etc). So, either my understanding of this isn't quite right (highly plausible) or they had a pretty major grid-level incident going on. Interesting that the various electrical breakers in the park didn't trip.
Thankfully no-one was hurt, but that's a fascinating story. I wonder if we'll ever hear any more...