Stray current

He was lucky to survive and most unusual if you survive to tell what it feels like, milliamps can kill you.
Prof. divers will not dive a boat when it's plugged in or running on gen set or with depth sounder on.

Please read the basics.

Marine Grounding Systems | West Marine

..and further some simple knowledge, we're here to help.

Every diver I know of cleans boat bottoms with the boat plugged in. It's a very very rare occurence that any electricity will be in the water like that.

Agree with Capt J. I've never seen a diver ask to have a boat unplugged. I've felt stray current in the water a few times, generally from dock wires that get submerged. No big deal. Feels tingly, itchy. There's a lot of water available to disperse the current in. Definitely not saying jump in next to a live wire, but if a wire goes in in Boston you don't get electrocuted in NY.

Perhaps if divers would read PADI guidelines for divers on this issue, it may save a life or two and maybe a lawsuit saving your family fortune...YMMV

agreed. but it does happen ... unfortunately ...

Awareness About Electric Shock Drowning - Seaworthy Magazine - BoatUS

and a couple of articles worth reading ...

Electric Shock Drowning (ESD) Explained - Seaworthy Magazine - BoatUS

http://www.boatus.com/seaworthy/assets/pdf/marina-dock-safety.pdf

Can you find an article stating the last time someone was electrocuted, diving underneath a boat? I'm sure it has happened, but you have better odds getting eaten by a shark in a marina, which again is practically unheard of.

This reads as a freshwater problem?
Very sad when the cause can so easily be avoided as per Maxpower's links.

Questions for the electrically minded; if a shore power lead is connected with a circuit breaker on the switchboard, would a leak from the dock/pontoon not trigger the breaker?

Also, regarding the generator running while diving, something I have never concerned myself with or read in the PADI training (Rescue Diver level) there is this in the link Awareness About Electrical Shock:
"Note that 12-volt electricity will not cause ESD. Nor will 120-volt current from a boat's generator unless another boat (with an electrical fault) is sharing electricity from the generator via a power cord."

If a freshwater boat is fizzing that much. Boy, you'll know it.

A good ground on your genset and all the outlets should be fine.

Growing up on salt water

This thread has prompted me to do a little digging. Spending my life on salt water, this was never considered a problem. Evidently that's because salt water is a good conductor. Fresh water is not, and the current would prefer to pass through a body. As I mentioned earlier I've felt current in the water, but it was nothing more than a tingle. I'll be a lot more cautious in fresh water in the future, although there's not a ton of precautions you can take other than don't swim near marinas.

Electric Shock Drowning Preventation Association

Read the News page.

http://www.qualitymarineservices.net/electric_shock_drowning_incident_list.html

http://www.mikeholt.com/newsletters.php?action=display&letterID=1309

Follow the links provided earlier:

http://www.electricshockdrowning.org/USCG_Grant_2008.226165406.pdf