Stray utility current could flow through this splash pad.

Someone didn't think that one through.

even with a garden hose at full flow i don`t think you would be able to get an arc or do something

if they were real issue you would see lots of kids toated in back yard here and there

well, most likely that water is being filtered and recycled and chlorinated. It is not pure de-ionized so there is a chance it can be conductive. One would hope that the overhead conductors are at least covered as in tree wire as it looks like those are water cannons. Someone could get the idea to see if they can hit the lines the same way here with deer season starting and frustrated hunters blasting porcelain insulators on our 46kV lines...polymers aren't as exciting to shoot....

If stray current is the concern as stated in original post, it seems there is some kind of common neutral overhead, perhaps several of them. The configuration phase spacing and number of conductors is not what I am familiar with.

You are correct .This is a 4 wire high voltage distribution system.The high voltage neutral is grounded at every 4th pole.Just beside this splash pad there are pole mounted step-down transformers with both the low and high voltage neutrals grounded at the base of the pole.Stray high voltage neutral current could be injected into the ground at this point and flow through this splash pad area (and the children).
Dairy farmers in Wisconsin are seeing this stray current flowing through their automated milking stations(the cows are getting zapped on their udders each time and are refusing to get milked and drink.)These farmers have successfully sued (for $$ millions) the utilities for this stray current problem after losing their entire herds.

I know cows don't like electricity at all.

I worked on farm equipment for a while after I first got out of the Air Force. We did an installlation of a computer feeder system. A few days later the farmer's wife called the shop and said she was getting shocked off the sink.

I went out to investigate and found the power strip at the farmers desk had a separate ground, so I ran a ground wire back to the service. When I applied power to the circuit, the power strip exploded. It seems there was a direct short to ground and it had been feeding 120VAC directly into the ground. There was voltage (about 4 or 5V) on the plumbing and on all the metal fencing.