Boston Mayor Marty Walsh chastised the operators of a cruise ship that was seen in Boston Harbor this weekend, seemingly packed with revelers.

During a press briefing Tuesday, Walsh said Boston and Massachusetts have come too far in bringing down the rate of COVID-19 infections and deaths to jeopardize that progress now.

"We've had our own struggles in the last five months where we had to shut everything down, people out of work, people having to socially isolate in your apartment — it's difficult. It, it wears on your brain," Walsh said.

"If we don't want to return back to that, we need to continue to be very vigilant. That cruise going out in the harbor that night was not very well thought out."

Walsh said the city doesn't have jurisdiction over the harbor. State officials ordered cruise operator, Bay State Cruise Company, to halt any further cruises.

Walsh also spoke about the rapidly-approaching, and still-uncertain, September start to the school year, both for Boston Public Schools and for students at Boston colleges and universities.

Walsh said he remains concerned about the impact on Boston of an influx of students this fall.

"I'm certainly concerned about the thousands of young people coming to our city, especially from areas around the country that are experiencing recent surges in COVID-19 cases," Walsh said.

The mayor said he has been meeting with the heads of some Boston colleges and universities and that any that choose to allow students back to campus will have to have plans for testing, quarantine or isolation, or other safety measures as necessary.

As for Boston Public Schools, Walsh said he still doesn’t know whether, how or to what extent, BPS students will be able to return to physical classrooms. Ultimately, those decisions will depend on the numbers for COVID-19 infections, Walsh said.

But the mayor said he is hoping to be able to implement a “hybrid” model that would balance precautions with giving students access to the educational, social, and emotional benefits of in-person learning.

"We are looking at a hybrid model that would assign students to groups and bring students to school on a rotating basis. That is what we're looking at today," Walsh said.

"But no matter what model is chosen, the Boston Public Schools have a fully developed plan for all-remote instruction as well, if the [COVID-19] cases go up."

"It's not one-size-fits-all," Walsh said. "All I know September 10, it will be almost six months that students have not been in the classroom."

Meanwhile, Walsh is urging Boston residents to fill out 2020 Census forms online. So far, the city's response rate is lagging significantly behind the 2010 Census -- and Census numbers help determine not just representation but various streams of federal funding the city relies on, Walsh said.

The mayor also reminded Boston residents that they will be allowed to vote by mail in the coming September and November elections, and can apply for mail-in ballots online via the city's Elections department.