But humpbacks aren't the only whales here. On the Big Island, Dan McSweeney operates a year-round whale-watching boat, the 42-passenger double-decked Lady Ann, to search for several types of whales found in Hawaiian waters, including humpbacks, sperm whales, Hawaiian pilot whales, Hawaiian melonhead whales and killer whales.

"It's something very few people realize," said McSweeney, who has spent 30 years studying and observing marine mammals. "They know about the larger species, primarily because the humpbacks come in so close to shore. But six other species of whales ... feed in these waters all year long."

Sighting a whale for the first time — or the 101st — routinely elicits shouts of joy, said Gregory D. Kaufman, Pacific Whale Foundation president. But often afterward, he said, "people are just dead quiet. They're almost at the point of being scared witless; it's so amazing; these animals are so large. There's nothing to say at that point."

Tori Cullen, a marine biologist who, with husband, Armin, leads whale-watching tours off O'ahu's Leeward Coast, said she's seen groups fall into a kind of meditative state when the 32-foot sailboat Hoe Hele is bobbing peacefully, engines cut off, near a pod of whales, and the animals are surfacing and blowing.

"It's just fluid — a kind of water ballet — and people respond to that," Cullen said.

To go out without finding any whales, as we began to fear during the uneventful first hour of this trip on the Ocean Spirit, is to be "skunked." With at least three whales appearing and disappearing on both sides and ahead of us, we are far from that.

Between sightings, we grow silent, heads swiveling, watching for a blow or a "round out" — a rolling movement that exposes a length of glistening, rubbery whale skin. When the animals surface, we can clearly hear their damp breath. When they dive again, the patches of white on their flukes and fins appear as a startling turquoise through the refracting water. "Captain Steve," as he's called, gently reminds us that we shouldn't all crowd to one side of the boat or clamber onto the upper deck.

"I think we've got a competition pod," said Brian Dobruck, the guide for this midday excursion sponsored by the nonprofit Pacific Whale Foundation. He means a group of males battling for supremacy in the presence of a female.

Whales active during season

The behavior of amorous humpback whales can make an awe-inspiring show: 45-foot bodies hurled almost free of the water to crash down again with a tremendous splash; notched tails as wide as your living room slapping into the water; charging heads slamming into each other. Dobruck has seen whales spout pink during these battles, the equivalent of a bloody nose.

Today, though, very early in the whale season, the action is relatively tame: surfacing, rolling, fluke-flipping.

No one protests when Captain Steve said we'll be late turning back, because we have to let the whales move on before we can get under way. We are, quite simply, enchanted.

As we should be, Kaufman said.

"As a scientist who began studying whales in the mid-'70s, I've always seen whale-watching as an opportunity to sing for our supper, an opportunity for us to interact with people, give them the latest information on whale conservation and let people become advocates for the whales," Kaufman said.

Because, unlike most marine creatures, these mammals are readily seen from the surface and make such a powerful impression, he said.

"I think humpback whales have been the greatest ambassadors for the ocean in terms of pure experiential education for the general public. They give personality to the ocean."

The Pacific Whale Foundation, centered on Maui, leads a series of "eco-adventures," including 15 daily whale-watch tours during humpback whale-sighting season, with proceeds helping finance marine education, research and efforts to protect whales, dolphins and coral reefs. Guides also keep a record of every whale sighted: when, where and behaviors observed, a growing database.

The PWF excursions are among the least-expensive at less than $25 per person, and are rather bare-bones (they offer drinks and snacks for sale aboard, and trips last about two hours). Longer half-day excursions with meals and other cushy amenities run from about $50 to more than $100 per person. Some offer money-back guarantees, or free tickets for a later excursion if you don't see a whale.

PWF's specialty is information; all its guides have been through at least a five-week naturalist training course. PWF also maintains an information station at the scenic overlook on Papawai Point from

8 a.m. to 4 p.m. daily during humpback season, to track whales visually and help keep its boats appraised of whale activity. (Beyond that, many of the Maui boat captains keep in touch with one another via cell phone during cruises, sharing information readily.)

Aboard the Ocean Spirit, Dobruck, who has a degree in biology, reels off the impressive statistics: The whales' pectoral fans average 15 feet long, their weight about a ton per foot — averaging 430 tons for the male, 450 for the female.

While in Hawaiian waters, the whales focus on procreation. The males posture and fight to intimidate competitors, then mate with females, who give birth here because it's warm. (They may also mate en route.)

Humpbacks are baleen whales, filtering seawater through rigid strips of keratin (similar to human fingernails) in their upper jaws, Dobruck said. They eat nothing for the four or five months they are here because there is nothing for them to eat: The tiny fish and krill (small crustaceans) that form the major portion of their diet are not available here.

Whale population growing

One reason that the whale-watch industry is booming is that there are more whales to watch. Since 1966, when commercial whaling was outlawed, the humpback whale stock in Hawaiian waters, which had declined to between 600 and 1,000 animals, has blossomed to the current estimate of 9,500 to 12,500 humpbacks. Cullen said she used to have to sail to Ka'ena Point to be sure of seeing whales; now, she said, "we rarely have to leave the coast to see whales."

Even so, Kaufman describes himself as only "cautiously optimistic" about the animals' future. The whales are doing fine, he said. It's people he and others are worried about. People produce increased boat traffic, marine debris and water pollution; they hunt whales for food and they interfere with their habitat. The boat traffic problem includes the behavior of whale watchers, who are supposed to maintain a distance of 100 yards from any whale they can see.

However, there are ways to get around this law — including the popular practice of estimating the direction a pod is moving, speeding around it and then slowing ahead of it, so that the whales swim toward you. "If they come up to you, that's OK, because they don't know anything about the rules," said Captain Steve, who does not engage in this practice.

Cullen worries that whales are becoming accustomed to having boats around, even becoming friendly. "They're losing their fear, and there are countries that want to go back to legalizing whaling because they need the food. That's a concern," she said.

Captain Steve said most experienced captains believe whales react to nearby vessels on an individual basis: Some are attracted, others repelled. Some boats have a reputation — perhaps based on the way they sound — for being whale magnets. Captain Steve's philosophy is to go gently. "I drive like an old guy," he says. "I'm easy on their ears."

Kaufman said land- and air-based whale observation studies indicate that the captains aren't far wrong. Some whales change behavior when a boat is nearby; some do not. But if they change behavior, they'll resume whatever they were doing when the boat leaves again, he said.

Kaufman knows of five collisions with whales in Hawaiian waters in the last year. His organization favors guidelines that would keep all vessels in Hawaiian waters to 20 knots (23 mph); 14 knots (16 mph) when whales are visible. He and others also favor developing cautionary practices and requiring training for those who take small watercraft near whales — inflatables and kayaks.

McSweeney said he believes the real problem in trying to effectively regulate recreational activities around marine mammals is a lack of knowledge. "We're a land-based animal trying to evaluate the behavior of a marine creature," he said. "Even if the federal government had unlimited funds to look at the issue, we'd still be scratching our heads saying we don't really know what we're doing."

Cullen, who pointed out that we don't even know for sure why or how humpback whales migrate, agreed: "The more you're out there, the more you know that you have no idea what's really going on with these animals."