From the Hudson to the East River and beyond, millions of people will hit New York’s waterways this summer.

“You’ve got tugs and barges and ferries and sailboats and kayakers and all these amazing individuals using it for their own purposes,” Donald Rotzien, director of community sailing and operations at Hudson River Community Sailing, said.

Rotzien teaches people of all levels to sail at Pier 66 in Chelsea.

“That’s one of the amazing benefits of operating as we do in New York Harbor is you’ve got marine police like Harbor Charlie,” Rotzien said.

“You definitely want to know what you’re getting yourself into before you start navigating these waters,” NYPD Harbor Unit Police Officer Mark Landi said.

The NYPD invited NY1 to check out its Harbor Unit at Brooklyn Army Terminal as officers anticipate a busy boating season.

“New York City Waterway is very large. We have approximately 526 miles of coastline,” Landi said.

According to Landi, people often find themselves in trouble due to a lack of knowledge.

“We can’t stress it enough. Just know the capabilities of yourself,” Landi said.

The unit recently assisted in a river rescue by helping three men stranded on Columbia Rock in Inwood this past May. The unit has five bases across the city.

“We’re not a unit that responds when a call comes in. We’re already out there patrolling, just like a regular police car does,” Landi said.

As police keep a watchful eye, Michael Petitie, co-founder of Manhattan Community Boathouse, said there’s no better time than now to get into the water.

“The water’s never been cleaner, so it’s a fantastic time to take advantage of this great opportunity,” Petitie said.

As people of all abilities make use of the riverfront, Petitie said it’s not just knowing to wear a lifejacket or how to swim, it’s also about knowing the water.

“Depending on that day, the tides change and it’s a constant cycle. So, if your plan is to go north at low tide, you’re going to wind up south of the Statue of Liberty. And so if you’re not planning according to those tides, you’re going to wind up in trouble,” Petite said.

The NYPD also stressed that waterways are not for swimming, there are the beaches for that. The rivers have high currents and personnel have seen waves at times up to four feet high.