Developers have begun building a ferry terminal on the raw, palm-lined shore of Treasure Island, the site of a massive real estate project that could bring 8,000 homes and 24,000 new residents by 2035.

The ferry is a critical element of the transportation plan that city and county officials are continuously refining to get people to and from San Francisco without jamming the Bay Bridge. Construction of 266 homes began earlier this year on the adjacent Yerba Buena Island, and within two years people will start moving in.

In addition to the new housing, Treasure Island will have retail, restaurants, a hotel and extensive open space, so officials are also planning for tourists to visit the new development and parks.

Though the project at this point is little more than a barge and a jumble of cranes in front of the Treasure Island Administration Building, it’s “almost the creation of a place,” said Chris Meany, co-manager of Treasure Island Community Development, a joint venture of Lennar Corp., Stockbridge Capital Group and Wilson Meany. The group is investing tens of millions of dollars to fund the terminal, which developers hope to open in 2021.

Meany and others see ferries as a form of mass transit infrastructure that’s at once romantic and utilitarian. It strengthens San Franciscans’ connection to the water, while overcoming the psychological barrier of the bay and the bridge.

“Treasure Island is a funny thing,” Meany said. “It’s five to 10 minutes to get (from there) to the Financial District, or 20 minutes to get to the west side of town. It’s super close. Yet, because it’s an island, it seems so distant.”

It’s unclear whether a public agency or private contractor would operate the ferry service, or whether it could eventually expand to other parts of the East Bay — which would largely depend on demand and population density. San Francisco County Transportation Authority hopes to start by running vessels from the island’s western shore to the Embarcadero every 30 minutes during commute hours. By 2035, ferries would run every 15 minutes throughout the day.

Additionally, officials are planning to ramp up bus service and replace knotty, potholed roads with a grid of freshly paved pedestrian paths and bike lanes. They’re also contemplating tolls to enter and exit the island, a form of congestion pricing that’s captivated transportation experts and sparked debate in City Hall.

Ferries may ultimately be the most desirable form of transport, with San Francisco’s waterfront a quick jaunt across the choppy waters of the bay. The Bay Area is the country’s third-largest market for ferry service — behind Seattle and New York City — and many politicians are eyeing a future that includes the ambling boats of the past.

State Assemblyman David Chiu, D-San Francisco, is particularly smitten with ferries. He pressed for $300 million of the Regional Measure 3 toll hikes to be invested in new ferry infrastructure, along with $35 million annually to support operating costs. Among the recent developments is a temporary landing in Mission Bay to serve the Chase Center.

Also on the horizon: a new ferry terminal at a 68-acre waterfront development on Alameda Point, formerly home to a naval air station. Officials will celebrate the groundbreaking of the Seaplane Lagoon terminal — the city’s third such piece of ferry infrastructure — on Thursday.

Like their counterparts on Treasure Island, developers and politicians in Alameda see water transit as a means to ease congestion, lure people out of cars and mitigate climate change.

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan