TALL ORDER: Newer cruise liners are too tall to pass under the Sunshine Skyway.

In 1998, Carnival Cruise Lines had to modify its 2,600-passenger ship, the Sensation, to squeeze under the Sunshine Skyway bridge and reach the Port of Tampa. Today, as cruise lines race to build bigger ships, the 187-foot-high bridge is proving a more formidable obstacle.

Since Carnival Cruise Lines first docked there in 1994, the Port of Tampa has become one of the fastest-growing cruise ports in the country. Approximately 730,000 passengers set sail from Tampa last year, generating 20% of the port authority's operating revenue. Conservative industry estimates peg the economic impact at about $60 million. But "further growth will be more difficult to achieve," Port Director and CEO Richard Wainio says, because "limitations posed by the Sunshine Skyway prevent the largest and newest vessels from entering the port, and new construction is heavily skewed toward these larger vessels."

Despite its height limitations -- official vertical navigational clearance is 175 feet -- the Sunshine Skyway can accommodate the "vast majority of the world's cruise fleet," says port authority director of public relations Lori Musser.

Wainio is optimistic that the port will be able to attract "at least one" additional home-ported vessel and that its passenger counts will reach 1 million by 2008.

In the meantime, the port is moving to mitigate another obstacle for cruise ships and other vessels that come into the upper part of the harbor. By March, it will complete the dredging of 81,000 cubic yards of material in Sparkman Channel.