Vessel-whale collisions are a concern for other large, fast ships operating in Hawai'i waters.

NCL America said its 921-foot Pride of America cruise ship follows NOAA and Pacific Whale Foundation guidelines. Passenger liners generally cruise at 20 knots, about 23 mph, but while crossing the Hawaiian Islands Humpback Whale National Marine Sanctuary, the NCL ship does not exceed 12 knots, the company said.

Bridge officers are familiar with NOAA whale-avoidance procedures and use a two-bridge officer watch system, with a pilot/co-pilot and a lookout, according to NCL. Night-vision binoculars are used to spot whales in the dark.

Matson container ships, which range in size from 680 to 860 feet and cruise at 24 knots, avoid whale sanctuary waters year-round, according to company spokesman Jeff Hull.

"We have a policy that regardless of season, our container ships do not sail through sanctuary waters. We either go north or south to avoid the sanctuary," he said.

Matson's interisland barges do cross sanctuary waters but are traveling at only 9 knots, he said.

Hawaii Superferry's Alakai cruises at just under 30 knots, slowing to no more than 25 knots while in the sanctuary and in the shallower waters of 600 feet or less that are preferred by humpback whales.

Unlike larger cruise and container ships, the 350-foot Alakai is highly maneuverable and able to change course or come to a full stop in a shorter time and distance.

The smaller Expeditions ferry cuts through sanctuary waters between Maui and Lana'i.

That 65-foot vessel travels at 20 knots, with both crewmen serving as lookouts, said Capt. Alan Steed. When a whale is spotted within 100 yards of the ferry, the vessel is brought to a full stop "and floats there until we can see that it's moved out of range," Steed said.

Expeditions was involved in a 2005 collision with a whale. And Steed said he was involved in a separate incident about seven years ago but is not sure whether the ferry hit a whale. The captain said he heard the engines make an unusual grinding sound and then spotted blood in the water, but never saw the animal.