The ones with the problem are aluminum in salt water, typically the "elevator" style where the frame is always in the water.
I would not own one, simply because of the marine fouling problems but people do.
I think the real answer is to separate the <service> bonded parts from the part that is in the water by double insulating the motor or electrically isolating it from the frame.
That is something that would have to be coordinated between U/L and the manufacturer I suppose.
I think on an existing installation I would start by making sure my electrodes at the house are doing their job. This may not be as big a problem when the electrode is a city wide metal water system. Folks up north may not really see it that much. I suppose if you drove additional electrodes down near the dock it would mitigate voltage differentials but dissimilar metals in the electrolyte (salt water) might create it's own problem. Do they make aluminum ground rods
