Numerous swimmers die each year after being subjected to electric current in the water from faulty wiring—but it isn’t electrocution that kills them. It’s drowning. This happens in swimming pools and hot tubs and also in water near ­marinas and docks.

What happens: Faulty pool wiring or faulty dockside or boat wiring or connectors allow electric current into the water. Even if this current is too weak to result in electrocution and death by itself, it still can cause a loss of muscle control, leading to drowning. Exactly how many people are killed by “electric shock drowning” (ESD) is not known—these deaths often are recorded as ordinary drownings with no one realizing that an electric current played a role.

New rules were added to the National Electrical Code (NEC) this year that require marinas to have ground-fault protection. Ground-fault circuit interrupters (GFCI) will immediately cut off the electric current when they detect an imbalance in the current flow. But these new rules apply only to docks constructed during or after 2017.

What to do: Do not swim in ­freshwater within 100 yards of a marina. The danger is greatest near marinas where there are dozens of boats and boat slips, any one of which could have a wiring problem. The risk for ESD is lower in salt water. (Salt water is more conductive than the human body, so any electric current is likely to go around swimmers, not through them.) Also…

•If you have a dock, pool and/or hot tub installed, hire a certified electrician to handle the wiring and to inspect it annually. If you own a boat, a certified electrician should annually inspect its wiring as well. Confirm that the electrician is certified to American Boat and Yacht Council standards.

•If you swim in a community pool, confirm that this pool is regularly inspected by a certified electrician.

•If you experience a tingling sensation, painful electric shock and/or diminished muscle control while swimming, get out of the water immediately if you can and warn other swimmers.

•If you see someone struggling to swim near a marina or boat dock, resist the urge to jump to the rescue. Instead, throw this person a flotation device and shut off the electricity nearby. ­