Shore power cords make an important and often unrecognized contribution to boating convenience. These flexible power cords make the connection between marina utilities and your vessel's power distribution system. Improper use and poor maintenance can cause serious injury or death, damage to vessels and unplanned repair costs.
 Two of the most popular flavors of shore power are 30 ampere 125 volt (NEMA L5-30) and 50 ampere 125/250 volt (NEMA SS-2) configurations. Power cords are designed to avoid mix ups between different types of plugs. The basic concept is to not force a plug into a receptacle. As long as the L-shape terminals of marine shore power plugs remain unaltered, it is hard to plug your boat into the wrong type of shore power. Forcing a modified 30 ampere 125 volt plug into a 50 ampere 125/250 volt receptacle can produce disastrous results.
 Forcing the wrong type of shore power plug into a receptacle or using a makeshift plug can inadvertently allow current to enter the water. Alternating current leakage into the water will often not open protective circuit breakers and will endanger anyone who might be in contact with the water. Leakage can also cause damage to boats and marina docks and mooring systems from electrolytic corrosion. A bad neutral or ground wire in a single boat can result in electrolysis throughout the marina showing up as excessive zinc wear or worse; damage to outdrives, propellers, struts, rudders and thru-hulls.
 Current leaking into salt water poses less of a problem that the same current being discharged into fresh water. Salt water is conductive and will carry current to earth ground. Fresh water is a poor conductor and leaking current will set up an electrical field around a vessel that is dangerous to swimmers. An amazingly small amount of current can paralyze a swimmer and cause drowning.
 Corroded power cord terminals are a sign of either salt water corrosion and/or the result of drawing too much power from the cord. A new 30 ampere cord typically can be used to draw about 20–25 ampere; drawing more power even temporarily, can alter the chemistry of the terminal ends through heating. The result of overdrawing current from a cord is that it will become more resistive to current flow and will require more current to supply the needed power for your boat.
 Think of a water hose with a slight bend in it, to get the same volume of water from the end as a hose without the bend, you will have to provide more pressure at the source. Winter customers can see significantly higher electric bills due to the use of older, corroded power cords.