Washington ? New antiterror rules could bring unreasonable costs and mean delays for family-owned ferries, sightseeing cruise lines and riverboat casinos, and perhaps drive smaller companies out of business, maritime industry officials said.

As proposed, the rules would require ships that carry at least 150 passengers to pay for extra security and maybe to screen all passengers, cargo and baggage. The Coast Guard has left open the possibility of extending the rules to smaller vessels as well.

“If we have to treat people the way you treat people at the airport, then our business is done,” said Alan Circeo, whose family operates A.C. Cruise Line in Boston. “We’re in the entertainment business. Our competition is local restaurants, theaters and museums.”

Under a law enacted last year, many U.S. coastal facilities, ports and ships must develop security plans by July 2004 and pay for guards, alarms, cameras and metal detectors.

The Coast Guard will release interim rules next month; after more public review, they will become final in the fall.

“We understand that the costs of security can be seen as overwhelming,” Coast Guard spokeswoman Jolie Shifflet said. “However, we do believe we’ll be able to develop flexible measures to ensure that our maritime system is secure.”

The SeaStreak commuter ferry Liberty leaves the dock in South Amboy, N.J. Family-owned ferries, sightseeing cruise operators, riverboat casinos and others in the maritime industry warn that new antiterrorism security measures could possibly drive smaller companies out of business.

More than 2,100 people attended seven public hearings on the proposed rules in January and February. The Coast Guard received 936 pages of written comments, many of them skeptical.

“We all know we live in a different world than we did a couple of years ago,” said Gary Frommelt, president of the Passenger Vessel Assn.

“Generally speaking, however, you’re not going to be able to turn a passenger vessel into a weapon of mass destruction on the magnitude of an airplane. To put the full impact of these regulations on some of our operators really means they’d go out of business.”

Before the attacks of Sept. 11, 2001, Congress was working on regulations to target theft and smuggling at ports. After the attacks, lawmakers turned the bill into a broader maritime security law that reflects enhanced security measures imposed on international shipping.

President Bush signed the bill into law in November.