What the hull?

Mayor de Blasio said Thursday he saw no serious safety issues with his foundering ferry fleet — claiming that two groundings in little more than a month weren’t a sign of danger to passengers.

De Blasio blamed both fateful trips — including the one that stranded 23 passengers on a sandbar off the Rockaways for nearly six hours Wednesday night — on “human error,” but insisted they were overshadowed by demand for the ferry service.

“There’s no question it’s safe. We have ample evidence it’s safe, and we’re going to continue to make sure the service is run well,” he declared at an unrelated news conference at NYPD headquarters.

“I have no idea why in these two instances specifically these mistakes were made… but you guys, you gotta look at the totality of something that’s now been going on quite a while and has a huge number of riders.”

Officials wouldn’t say who was at the helm Wednesday. The city’s Economic Development Corp. — which arranged and oversees the NYC Ferry service — said the unidentified captain “has been taken off duty pending the outcome of the investigation.”

Co-workers told The Post the captain hadn’t piloted an NYC Ferry boat for some time before Wednesday and may have been unfamiliar with the waters where he ran aground.

The captain was brought in to replace the route’s regular captain, an experienced mariner known as “Danny,” who called out ahead of his Wednesday shift, one worker said.

“Danny’s really good. He wasn’t driving. He usually drives,” the worker said.

The captain who plowed another NYC Ferry boat into an underwater pile field in the East River on Nov. 27 — previously identified by sources as Michael Sabatino — hasn’t returned to the helm and is currently assigned to other duties, the EDC said.

While de Blasio insisted he didn’t consider either incident “acceptable,” he noted that no one got hurt — and suggested it was “ample evidence” that riding NYC Ferry boats wasn’t dangerous.

“People are safe because people all came out of it safe. That’s the answer,” he said about Wednesday’s incident.

Rescue efforts stretched into the night because water in the area was so shallow that the passengers and crew had to be shuttled on inflatable dinghies — in windy temperatures in the mid-teens — to an FDNY boat.

The mayor also downplayed the corrosion and leaks that sidelined six ferries last month — as exclusively revealed by The Post, and initially denied by City Hall — as “a few issues with a few boats.”

Only one of those boats has returned to service, with repairs to the others “nearing completion,” according to the EDC.

De Blasio also repeatedly pointed to the popularity of the maritime commuter service that began operating in May with $325 million in taxpayer subsidies.

“We’ve had a huge level of demand for the ferries. They’ve worked well,” he said.

“There were times where we had too much demand, and we had to adjust and we did adjust. Safety has not been a problem here.”

The captain in Wednesday’s incident strayed about one-third of a mile off course shortly after leaving the Rockaway terminal at 5:15 p.m. en route to Wall Street’s Pier 11, sources said.

“That’s something investigators will look at during the investigation,” Skye Ostreicher, a spokeswoman for ferry operator Hornblower, said in a prepared statement.

“Safety is our number one priority, and we will continue to review our training programs in order to ensure rider and crew safety.”

The ferry, named the Flyer, was in dry dock yesterday at the North River Shipyard in Upper Nyack.

It won’t carry passengers again until it’s been inspected and cleared by the US Coast Guard, the EDC said.

Hornblower is trying to make amends by giving each of Flyer’s passengers a yearly ferry pass, a $50 Uber credit and a dinner-and-movie package at the iPic Theater at the South Street Seaport.

Three Rangers fans who were headed to Madison Square Garden to watch the Blueshirts take on the Washington Capitals — but missed the game — will also be reimbursed for the cost of their tickets and receive reservations for a future game, the company said.

The National Hockey League is also treating the trio to six tickets to the NHL Winter Classic game between the Rangers and the Buffalo Sabres on New Year’s Day, along with a VIP tour of preparations at Citi Field.

League exec Keith Wachtel said he decided to bestow the “belated Christmas gift” while reading about the fans’ misadventure in The Post during his Thursday morning train ride.

“They were wearing Rangers jerseys and realized they missed a great 1-0 Rangers win in their first game back from the holidays,” he said.

Additional reporting by Shawn Cohen and Amanda Woods