PASSENGERS DEPARTING FROM THE

HARBOR EACH YEAR.

THAT MAKES IS ONE OF THE

PRIME TARGETS FOR THOSE WITH

BAD INTENTIONS. IT IS PREDAWN

AND THE NORWEGIAN GEM CRUISE

SHIP IS MAKING ITS WAY BACK TO

NEW YORK AFTER 10 DAYS SC -- AT

SEA. THE SHIP IS NOW UNDER

SURVEILLANCE AND BEING SWEPT

FOR A DIRTY BOMB BEFORE IT

ENTERS THE CITY LIMITS.

HOW CLOSE DO YOU HAVE TO BE

TO BE ABLE TO DETECT SOMETHING

WHEN IT COMES TO RADIATION?

Reporter: HUNDREDS OF CRUISE

SHIPS LIKE THIS TRAVEL IN AND

OUT OF THE PORT OF NEW YORK AND

NEW JERSEY EACH YEAR.

THE CRUISE LINES CAN ONLY DO SO

MUCH. AS THEY RETURN HOME

FROM FOREIGN PORTS, IT IS UP TO

THESE GUYS, A UNIT WITHIN THE

NYPD'S COUNTERTERRORISM DIVISION

TO ESCORT THE SHIPS IN SAFELY

AND WITHOUT INCIDENT.

IT IS EASY TO JUMP ABOUT AND

DO SOMETHING BAD.

THIS MORNING THERE WAS AN

ATTACK ON A SAUDI ARABIAN

FRIGATE IN THE RED SEA.

IT WAS A SUICIDE ATTACK.

Reporter: DEANN RICHARDS,

CEO OF GLOBAL RESCUE, A COMPANY

THAT PROVIDES CRISIS RESPONSE

AND EVACUATION OPTIONS TO

TRAVELERS SAYS DESPITE FEW

INCIDENTS TO DATE, TERRORISM

WITH RESPECT TO CRUISE SHIPS IS

NOT UNLIKELY.

WE KNOW THAT ISIS AND OTHER

TERRORIST ORGANIZATIONS ARE

PLANNING THESE KINDS OF

OPERATIONS.

THAT IS WHY WE ARE OUT HERE.

WE TRIED TO BE PROACTIVE.

Reporter: IT HAPPENED IN YEMEN

WHERE APPARENT SUICIDE BOMBERS

HAD -- BLEW A HOLE IN A U.S.

NAVY DESTROYER..

CRUISE SHIPS ARE NOT THE ONLY

SOURCE OF CONCERN.

NEW YORK HARBOR IS PACKED WITH

OIL TANKERS, CARGO FREIGHTERS

AND PASSENGER FERRIES ALL

FALLING UNDER THE SUPERVISION

OF THIS ELITE GROUP.

WE WOULD BE ABLE TO SCAN

THE.

TO SEE IF THERE IS ANYTHING

BELOW THE SURFACE OF THE

WATER. Reporter: MICHAEL

DELANEY SAYS THEY USE SONAR TO

SCAN THE PEERS DAILY.

WE OVERLAY THOSE IMAGES TO

SEE IF THERE WAS ANYTHING THERE

TODAY THAT WAS NOT THERE A FEW

DAYS AGO.

EVERYTHING IS UNBELIEVABLE.

WHILE THESE MEASURES MAY NOT

BE TOP OF MIND FOR CRUISE SHIP

PASSENGERS, NOW THAT THEY KNOW

ABOUT THEM, THEY SAY THEY

CERTAINLY APPRECIATE THEM. IT

MAKES ME FEEL VERY SECURE.