EXCLUSIVE: What it takes to keep NYC safe on 4th of July

GRAMERCY PARK, Manhattan (WABC) -- The East River may be the best spot in the country to watch Fourth of July fireworks, but Independence Day is no pleasure cruise for Sergeant Tom Horvath and his crew - part of a flotilla of law enforcement vessels on the water Monday night - watching everything but the sky.

"Our job is to find the guy who might not be looking up in that crowd, or a boat that maybe starts to wander because he thinks the police attention is maybe focused up there," says Sergeant Horvath.

About an hour before the Macy's Fireworks show, Eyewitness News got an exclusive ride on an NYPD patrol boat - whose crew will have to monitor dozens of pleasure boats, and also their own classified equipment on board.

Of more than 40 boats the NYPD has on its waterways throughout the five boroughs, Eyewitness News rode on none of two specially equipped with radiation detection - and this is just one piece of the puzzle.

Back on land, Chief James Waters explained how the department is constantly evolving. New this year, dogs trained in so-called vapor wake detection - that can sniff out someone who has merely handled explosives. In the wake of the Istanbul attack, there is a renewed focus on the areas before the checkpoints.

"That's something we've been focused on for a number of years. Wherever you put the checkpoint, if the terrorist is not going to be able to penetrate, that's gonna be what's most vulnerable," said Waters.

A huge show of force on the ground, on the water and in the are - the highest of stakes with more than a million and a half lives in the balance.

"It's very complicated, but the more you train, the more you feel prepared for it. I think we're prepared, I really do. We're as prepared as we can be," adds Horvath.