Hawaii Superferry announced yesterday that its interisland vessel has successfully completed sea trials in the Gulf of Mexico.

The trials by shipbuilder Austal USA are part of a review and testing of the systems, machinery and equipment aboard the four-story vessel set to begin service from Honolulu in July.

"Sea trials went very well and we are extremely pleased with the capabilities of this vessel," said Dan Spiegel, Austal's chief operating officer. "It's truly remarkable to experience the power and control of this catamaran.

"Completing sea trials in only five days and achieving or surpassing all performance parameters specified for the vessel is an excellent result."

Terry White, executive vice president of operations, called completion of the sea trials a "key milestone event" for the 900-passenger, 250-car ship built especially for Hawaiian waters.

"We are impressed with the vessel's performance during its initial trials and are confident that she will do well in Hawaiian waters," he said. "Our crew is looking forward to her maiden voyage and to bringing a choice of interisland travel to the people of Hawai'i."

The vessel will be christened Saturday in Mobile, Ala., where it was built.

Austal is expected to hand over the vessel to Hawaii Superferry at the end of the month. It will then make its way to Hawai'i via the Panama Canal in May.

Service between O'ahu and Maui and between O'ahu and Kaua'i is scheduled to begin in July with one-way fares of $42 per person and $55 per vehicle. A second daily route between O'ahu and Maui and service between O'ahu and the Big Island are to be offered in 2009 with the arrival of a second ferry.

Legislation that would have forced the state to complete a study of the interisland ferry service's impact on harbors technically died when it failed to meet a procedural deadline early in the legislative session.