FREEPORT — When the Heron entered the ocean for the first time Thursday afternoon, the sounds of a splashing wake and laughing crew overwhelmed the low hum of its motor. Moments earlier, as it idled along the dock, some asked if the motor was even running.

“It’s really disconcerting,” said Willy Leathers, co-founder of Maine Ocean Farms, an aquaculture company that commissioned the all-electric boat. “You’re taken aback that there’s no sound to the motor running when you’re clutching it in. … But it’s exactly the feeling we were hoping for of great performance on the boat.”

Leathers and a small crew, including project designers and advocates, puttered around the harbor for about an hour, weaving between anchored sailboats to test the craft’s speed and handling.

A project three years in the making, the Heron is among Maine’s — and the country’s — first fully electric aquaculture workboats.

“As far as I know, it’s the first fully electric aquaculture boat,” said Lia Morris, senior community development officer at the Island Institute, which helped develop and fund the boat and has advocated for similar projects for years. While a few smaller electric skiffs are being used by commercial fishermen and oyster farmers in Maine, she said the Heron marks the first electric workboat of its size.

The institute helped develop another electric boat a few years ago, but it was a small vessel with a roughly 40-horsepower engine, she said. The Heron measures about 28 feet in length and 10 feet at its widest point.

Beyond hauling oysters, the boat is intended to test and demonstrate the feasibility of similar projects, Morris said.

Its dual 120-horsepower offboard motors are powered by a pair of below-deck batteries, which together hold about 126 kilowatt-hours. And it can carry up to 4,000 pounds of gear and oysters, Leathers said. Fully loaded, the Heron can go 20-25 miles on a single charge, Leathers estimates, but that capacity will depend on factors like speed.

The Heron weighs about 9,500 pounds empty, said Patrick Fogg, designer and builder at Fogg’s Boatworks, the North Yarmouth shipbuilder that put it all together. He said the batteries alone are 1,600 pounds, and there’s another 300-400 pounds of cabling that would not exist on a gas boat.

“So you’re definitely heavier,” Fogg said. “Your batteries are probably about twice the weight of your (gas) fuel.”

COST CONSIDERATIONS

All told, the vessel cost about $400,000, about half of which went toward the welded hull and another half toward the batteries and powertrain, Leathers said. Part of that came from a federal grant from the Department of Energy, which will also fund a pair of level-three chargers in Portland and near the Freeport harbor.

“(That’s) not disproportionate to what you might have with a gas outboard installation. It’s probably just a little higher, in the order of maybe 50 grand,” he said.

Leathers said it’s not clear whether electricity will end up costing less than diesel fuel in the long run. He noted Maine’s higher-than-average electricity prices and the newness of its aquatic charging infrastructure.

“I’m reluctant to say that it will cost less, because it may not,” Leathers said. But “we can’t make all of our decisions only off of operational costs.”

He suggested that the new boat may need less frequent maintenance than more traditional vessels, which could cut down on additional costs. And, with the quiet motor and a hull that rides shallowly on top of the water, the boat could open up new revenue streams, Leathers said.

“The noiseless operation, we’re hoping that expands into a lot of collaborative potential with research organizations and stuff, because we won’t be having an impact on the marine environment beneath us,” Leathers said. “We’ll be quiet, even moving at speed. We can carry gear and equipment.”

Plus, unlike gas-powered vessels, battery-powered boats don’t directly emit greenhouse gases that contribute to global warming.

Hours before launch, as the boat swayed in a lift on shore, Maine Ocean Farms co-founder Eric Oransky gave a prechristening speech, riffing off a sheet of printed notes he had prepared before sunrise. Leathers stood to his side, peeling the foil off a bottle of sparkling wine.

The boat, he said, is named after Casco Bay, which the Abenaki called “Aucocisco” — a phrase that can translate to “place of the herons.”

“May Heron always find calm seas and safe harbors. May she travel lightly upon the water,” Oransky continued. “May all those who journey aboard her be enriched and inspired by the experience — ”

The cork exploded out of the bottle, cutting Oransky short and drawing cheers and laughter from the crowd. Leathers shook the bottle, held his thumb over its mouth like a garden hose and splattered foam across the boat’s metal bow.

“Now we get to test the wash-down pump,” Oransky joked.

Once in the water, the Heron needed just a quick charge — and software update — to get moving. Within minutes, it disappeared into the fog.