WASHINGTON – New anti-terror 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 say.

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.

In Maine, for example, Bay Ferries’ Cat, which runs between Bar Harbor and Yarmouth, Nova Scotia, can carry up to 900 passengers and 240 cars, according to its Web site.

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, which offers sightseeing, wedding and whale-watching cruises around Boston Harbor. “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.”

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 Association.

“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 2002.

The rules would force many domestic vessels, the nation’s 361 public ports and other piers, terminals and loading docks to comply with security protocols more typically associated with ships and ports involved in international seafaring.

Fishermen, tugboat operators and mobile offshore oil drillers are among those alarmed by the potential reach of the new rules.

“Fishing industry vessels and facilities are not likely targets of terrorist attack,” wrote a coalition of trade associations representing the fishing industry off Alaska.

People who have made a career on the sea – on cargo ships and passenger lines – worry the security rules would make it difficult to take shore breaks.

Riverboat casinos in Illinois, Louisiana, Iowa, Missouri and Mississippi emphasized their existing security and general lack of mobility in hopes of fending off a requirement that they screen all their guests.

Operators of mobile oil drillers asked that they not be classified as ships.

The Coast Guard estimates that affected ships, ports and other facilities will have to spend $1.4 billion in the first year alone to hire and train security officers and to buy equipment.

In addition, many commercial and passenger ships may have to install transponders so their identity and movements can be tracked continuously.

A new port security grant program distributed $92 million to 51 ports last year and will allocate another $105 million this year.

Government officials say the maritime industry must assume it is a target for terrorists.

“The threat is definitely here,” Adm. Larry Hereth, director of port security for the Coast Guard, said at a public hearing. “I can tell you it’s real, and it’s not going to go away.”