Electricity and water do mix, at least in Stockholm, where an electric ferry promises silent, low-emissions cruising and a unique rapid recharging system.

The Movitz, a 75-foot ferry that can carry 100 passengers, is undergoing a retrofit to electric power. When the battery-powered Movitz sets sail for Stockholm's Green City Ferries in August, its 335-horsepower diesel engine will have been replaced by two 125 kilowatt electric motors mounted outside the hull—one on each side, for ease of maneuverability.

Passengers won't have to wait for the Movitz to charge. A rapid charging system takes just 10 minutes to give the ship's 180 kilowatt-hour nickel metal hydride batteries enough juice to run for one hour at 9 knots. The system was designed by Echandia Marine, a startup founded by a submarine engineer with expertise in marine electrification.

Echandia says the conversion will cut 130 tons of CO2 emissions and 1.5 tons of NOx emissions while cutting operating costs 30 percent. The project is supported by the Swedish Energy Agency.

It makes sense to electrify a vehicle that travels a fixed route with long stops. Like delivery trucks and buses, a ferry has a predictable schedule. The Movitz will spend its days making hourlong journeys with 10-minute layovers in between for charging, while passengers are loaded and unloaded.

Ferries are a crucial means of transport in Stockholm, a city that's built across 14 islands. The Movitz will operate on a route between Solna Strand and Stockholm's Old Town.