IIRC the mythbusters experiment was regarding the '3rd rail' in the New York subway system
Dunno if their results would translate to the capacitor-charge/discharge system in a typical electric fence as the '3rd rail' is carrying 600 - 700 volts DC at fairly high amperages.
(Captain Placid 24/7 ball gags, brownie mix and clown porn, Tue 29 May 2012, 9:12, 2 replies)

I remember it being testing out if you could make a taser using salt water streams instead of wires. They found that a short distance out the stream broke into discrete droplets that the charge couldn't jump.

The problem becomes one of turbulent flow versus laminar flow. A single tube stream has varying velocities- faster toward the center, slower toward the outside- which make it turbulent. But if you use a bundle of small tubes in parallel, the turbulence tends to get canceled out and you get a smooth stream of water which can in fact be continuous for a long distance. Here's a video which may help: youtu.be/OV-IazRk0sU

Mythbusters didn't take it quite far enough. Given two laminar flow nozzles in parallel, you could indeed make a taser with saline as the conductors.
( The Resident Loon Not a demographic. Do not measure., Tue 29 May 2012, 9:54, closed)

It also seems more likely that
the stream could be starting closer to a high strand of an electric fence and not have time to break into the droplets that meant the third rail - which is at ground level - didn't shock them.
(richardm, Tue 29 May 2012, 17:32, closed)