Back in May, Mayor Bill de Blasio said ridership on the new municipal ferry service was so strong, larger vessels are on the way.

On Thursday, the city previewed the first of those new boats, as the service hit a milestone - five million riders carried since May 2017.

The double-decker Ocean Queen Rock Star took test runs in and out of the Brooklyn Navy Yard, where it's docked before going into service in two weeks.

It can carry as many as 350 passengers, more than double the capacity of the 17 existing boats in the NYC Ferry fleet, which can transport as many as 150 people each.

The vast difference in size of the ferries is especially visible on the the upper deck of the new vessel, which towers over those that were put into service earlier.

"What we learned early on was that this was an extremely poplar service. We're really thriving on the growing ridership and to help meet that demand, we really wanted to invest in our fleet to have those 350-passenger vessels available to us," said NYC Ferry Executive Director James Wong.

Demand has been especially heavy on weekends and holidays, with lines of Rockaways beachgoers sometimes stretching for blocks.

"One hour. Then I give up," said one eager rider.

Two more plus-sized ferries are on the way this summer. The three big boats can run on any of the routes in the new municipal ferry service, which will expand by September with service in and out of the Soundview section of the Bronx and Manhattan's Lower East Side.

"We're trying to make sure that when we do have high demand - like people trying to get out to the beach or whether they're trying to go to Governors Island or other places throughout the NYC Ferry system - that we're able to quickly meet that demand," Wong added.