"Babies breaching," someone shouted, and everyone rushed to the side of Sea Shepherd's Steve Irwin vessel, binoculars at the ready under the black Jolly Roger flag flapping in the breeze.
In the distance, several kilometres from the Dampier Peninsula coastline, an adult whale slapped her tail and blew plumes of water as her young calf playfully breached beside her, silvery in the early morning sun.
Kimberley naturalist Richard Costin pointed back to the coast, where red rocks loomed above bright white sand.
"We're just coming into the development area for the proposed James Price Point gas hub … (it) has the highest concentration of whales on the Kimberley coast," he said.
"From here through to the Lacipede Islands, the work that we've done in the last three or four years has pinpointed this area as being perhaps the most important area on the Kimberley coast for the whales.
"The whales are actually calving all the way along the coast … between the 80 mile beach and just to the north of Camden Sound. The calving grounds, up until now, have been totally undisturbed."
The whales were the first of 22 - including at least 10 calves - to be spotted today between Broome and James Price Point, the site of the State Government and Woodside's proposed gas hub.
For former Greens Senator Bob Brown, the sight proved his point: that the area was the "world's biggest whale nursery" and the wrong place for the development.
"This is a national whale sanctuary - here we are to protect it," Mr Brown said. "The whale nursery cannot co-exist safely with a gas factory. As a nation, we should be protecting it."
How many whales inhabit these Kimberley waters - and what effect the proposed gas hub will have on their annual migration from Antarctic waters in the south to give birth in the north- is proving the latest flashpoint in a long series of battles between those for and against the hub.
Woodside has said the most important calving ground for the whales are much further north in Camden Sound and that the impacts on whales passing by the proposed development can be adequately managed and mitigated.
Others - including the crew of the controversial anti-whaling vessel Steve Irwin - disagree.
Earlier this week, the vessel sailed into Broome to ramp up the campaign against the proposed gas hub by drawing international attention to whales in the region in a bid to embarrass those who are part of the project.
This morning, surveying the calm waters and blue skies, Captain Malcolm Holland admitted it was not the Sea Shepherd's typical kind of campaign Usually, the crew are in the Antarctic, dodging bullets, water cannons, acoustic devices and flash bang grenades in stormy seas, getting rammed by ships manned by the armed Japanese coastguard.
However, he sees the Kimberley action as just as vital, pointing out it involves the same whales.
"This is a very different kind of campaign … what we're doing on this campaign is showing what it's like up here - that they're building a heavy industrial facility and international sea port right alongside the biggest humpback whale nursery in Australia," he said.Despite the pirate motifs and camouflage paint all over the ship, the Sea Shepherd has a polite crew, reminded by signs all over the place of the strict rules: no drinking, no smoking, no fraternising, no shouting.
Visitors on board are also hardly an anarchistic bunch - among them, rich former Melbourne merchant banker Phillip Wallon, now an extremely wealthy philanthropist who has given millions of dollars to supporting the Sea Shepherd's cause.
This morning, he threw in an extra $100,000 and suggested others who could afford it should do the same.
"This is a battle that we just cannot afford to lose," he said. "10,000 entire species are wiped out every year because of the actions of one species … that is a crime of unimaginable proportions."
"I come from a corporate background. I am pro business … I don't want to shut anything down. But I also want to make sure that we take care of all the externalities - the costs that business imposes on communities and the environment must also be taken into account."
Retired Queens Counsel Murray Wilcox, said he was interested in seeing how close the whales intersected with the site of the proposed gas hub.
"It's obviously a very close relationship," he said.
He denied the Sea Shepherd was run by anarchists: "I think this is people who are very concerned about an issue that should concern us all," he said.
"I think the Kimberley is one of the most beautiful areas in Australia - certainly one of the most pristine areas - and we have an opportunity to preserve a fairly well untouched wilderness area.
"If we don't, there will be nothing left for our grandchildren. It is possible to exploit the gas reserves from the Browse basin without building a Kimberley gas plant."
Environs Kimberley spokesman Martin Pritchard agrees. He said research carried out by community volunteers had counted 1441 humpback whales passing through since July 1, 1200 within 8km of the shore.
However, he said the Environmental Protection Authority had stated that on their annual northern migration, about 1000 whales would be expected to go past during an entire season.
"In three weeks, just looking four hours a day, we're already had 1200 whales counted and about 90 cow-calf pairs," Mr Pritchard said. "It's actually proving Woodside and the State Government's research wrong."
Mr Costin said he had no faith in the research commissioned by Woodside and the State Government and even believes the results were deliberately fudged.
"When you look at the results at face value … the survey work … that is being relied on is totally unreliable," he said.
"And no-one really understands what effect the discharges from an LNG facility processing 50 million tonnes per annum would have on the marine environment."
Sea Shepherd Australia spokesman Jeff Hansen pledged that the ship would return to defend the whales in Kimberley waters for as long as it took to stop the project from going ahead.
"We do our best every year to save as many whales as we can in the Southern Ocean Whale Sanctuary in the Australian Antarctic Territory," he said.
"If the Australian government is not going to protect those waters, then the very least they can do is make sure that their largest humpback whale nursery is safe and protected, here north of Broome.
"If they're under threat here, then we're here to do whatever we can within the law to protect them here.
"People all around the world have the right to know that this is the largest humpback whale nursery and that the gas hub will go right through the middle of it."