Standing beneath that boat’s hull, Mr. MacRae joked about New York’s increasingly crowded waterways, saying, “This is the view we don’t want any kayakers to have.”

In a three-sided shed in Franklin, La., about 100 miles west of New Orleans, another boatbuilder, Metal Shark, has a team of 45 workers building four more ferries to match those produced by Horizon. To the untrained eye, all of the boats under construction look identical — except for three that will have deeper, wider hulls to smooth out the choppy waters between the Rockaways and the Wall Street dock in Manhattan.

When the ferries are finished, commuters will not be able to distinguish between the two companies’ products, said Josh Stickles, the marketing director for Metal Shark. “But we will,” he added, gesturing toward welders attaching aluminum plates to the inverted frame of a hull.

Some skeptics have criticized the city’s plan to make all of the boats 85 feet long with a capacity of 149 passengers, as opposed to having some larger vessels for the hourlong run to and from Rockaway. “Confusingly, they’re building 20 boats the same size,” Tom Fox, who once ran New York Water Taxi, said at a ferry conference in Manila last month.

Mr. Fox also questioned the city’s decision to charge riders the same fare that subway riders pay, which is $2.75 now but may rise next year. That is significantly less than the $4 it costs to ride the East River Ferry service that the city has been subsidizing for several years. The success of that service prompted the decision to expand it citywide and to eventually bring it to the Bronx and Staten Island.

But for now, city officials are concentrating on proving to skeptics that more than a dozen passenger ferries could be built in a year. Seth Myers, an executive vice president with the city’s development corporation, said he was impressed with the collaboration between the shipyards. “We’ve seen just a very energetic approach to delivering these boats on schedule,” Mr. Myers said.

Metal Shark has specialized in building sets of boats for government agencies, both domestic and foreign, Mr. Stickles said. When the company received the ferry contract from Hornblower, its workers were wrapping up a set of 18 sleek patrol boats for the Vietnam Coast Guard.