Why Swimming in Your Marina is a Bad Idea

Imagine: it’s a beautiful hot, sunny afternoon. You’re at your favorite marina getting your boat provisioned and equipped for a fun-filled weekend with your family. The sun’s shimmering on the water enticing you to dive in for a refreshing swim.

Don’t do it.

In the water of even the most pristine marina, there could lurk a silent and invisible killer – stray AC electrical current. Boats plugged into a shore power service at any given marina may have an electrical “leak” that could prove lethal.

It can happen more easily than you think, here’s how:

Electricity flows along the path of least resistance to complete a roundtrip loop called a circuit. Every time a boat is connected to shore power an electrical circuit is formed, flowing from shore to vessel and back again. Similar to hydraulics, this current puts “pressure” (called voltage) on the boat’s AC electrical devices and appliances. Any number of scenarios can cause a leak where some portion of this electricity may escape from its intended circuitry.

At best, the device’s safety ground (typically a green wire) will carry the leaking electricity back to the source and safely complete the circuit. However, because the AC ground circuitry is also connected to the boat’s bonding/grounding system (including underwater hardware), sometimes the path of lesser resistance is through the water.

When electricity is leaking through the water and flowing towards shore, a swimmer may become a better conductor than the water itself. This is especially true in fresh or brackish waters where the human body is inherently a better electrolyte solution, and therefore a better conductor than the surrounding water.

As little as 50 to 100 milliamps of electricity conducted through the heart can be deadly.

There are no visible signs to indicate stray electrical current, and therefore no way to know when one may be present. So, don’t take the risk; don’t swim in or near marinas.



– Glenn Campbell, Head of Engineering, Sabre Yachts

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5 Responses to Why Swimming in Your Marina is a Bad Idea

  1. bill thomas says:

    Very, very, dangerous to swim in a marina. Every year people die. We had an incident here in Michigan a few years ago where two people died, second one trying dove in to save a child. This is in fresh water too, not as conductive as salt water but still deadly.

  2. John Clark says:

    Our best friend’s son was killed this summer due to electric shock drowning after their dog fell in at a marina and they tried to save him not aware the dog was being shocked. It was at Miller’s Marine in Put In Bay on Lake Erie.

    Please heed this very sound advice

  3. bruce says:

    how about boat cleaning divers in the marina?

  4. Rae Kleinen says:

    Will a “Black Box” Isolater, professionally installed, limit this problem for my boat?
    Should I limit the time that I am connected in to AC Shore Power and a Inverter Charger
    on my boat? Just connecting the charger a few hours a week to top off the 6 batteries help limit this problem? .
    How does this stray electric affect my Anodes?
    Thank you, Rae

  5. Jesse says:

    I always practice and tell my friends the following rules when boating.
    1. Never swim near a marina
    2. Never swim near any boat ramps or close to open water where boat traffic is heavy!

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