You know it seems that a voltage leak test could be done using one of the $149.95 Shock Alerts, the larger yellow floating device that uses both a buzzer and a light, attached by a 6' line to a stand-up paddle board, and paddled slowly past suspect spots around the lake.
By paddling while kneeling on a sup, one would seem to be pretty much insulated and safe from any voltage leaks in the water because the sup is a fiberglass/plastic/vinyl non-conductor for 110-v electric current, and will block a pathway for electricity to flow.
Town docks and marinas that use ice-eating, water circulators for winter ice protection that leave their wiring out there, in place, all year around, are suspect for leaky stray voltage.
Boat lifts that run on 110-v current are also suspect.
And, according to the linked report in the above post #1, a running motor boat can put nearby swimmers in danger with a stray voltage leak coming from the boat? .....