With its distinctive pirate-like flag flying from the mast, the sleek, high-speed concrete grey Ocean Warrior is the latest weapon in a bitter war between marine conservationists and Japan's whaling fleet.

"The one thing that we were missing in our fleet was a vessel with speed and endurance," said Alex Cornelissen, chief executive of Sea Shepherd Global.

"With the Ocean Warrior, we have a ship that can outmatch any poaching vessel on the high seas," said Cornelissen, also the captain, giving AFP a tour of the ship before its departure from the Netherlands this weekend bound for Australia.

"We are now able to follow them anywhere they go and even run away if they become too aggressive."

Bought at a cost of 8.3 million euros($9.3 million) funded by public lotteries in Britain, The Netherlands and Sweden, Sea Shepherd Global is counting on the vessel in its upcoming battle to save the whales in the icy waters of the Southern Ocean.

The new vessel, designed by a Dutch shipbuilder, took 18 months to build. Stretching some 54 metres (yards), it is a state-of-the-art ship, equipped with hybrid propulsion to extend its range, four powerful engines and a helicopter landing pad.

But it also has a secret weapon -- on the bridge a red cannon can eject a powerful plume of water to obstruct the views of the whalers, or block them from boarding.

For almost four decades, Sea Shepherd has fought to "defend, conserve and protect" marine life in the vast expanses of the planet's oceans.

- Masquerading as science -

And for 30 years they have been playing cat-and-mouse on the high seas with determined and at times ruthless whaling fleets.

"The minute you actually find them, you get very excited and the whole crew is excited because that's what you came down here for," said Cornelissen, sitting at the controls which resembles the helm of a spaceship.

"And then you just go into this high energy mode. You don't get tired anymore. You can stay up for 24 hours without interruption," he added.

"All the sacrifices you made to be down in the Antarctic, you know, missing Christmas, missing your family, it's all become worth it when you find the whalers."

Despite a global moratorium imposed in 1986, Japan has continued to hunt whales using a loophole in the ban, but makes no secret the giant mammals end up on dinner plates.

Tokyo was forced to call off its 2014-15 hunt after the International Court of Justice, based in The Hague, ruled its annual Antarctic foray was commercial, and only masquerading as science.

But the hunt resumed in late 2015, with the fleet returning to Japan in March this year after having killed some 333 Minke whales.

Tokyo has sought to close down the anti-whaling campaigns in court saying the activists ram their ships, snare propellers with ropes and harass crews with paint and stink bombs.

The conservationists in turn complain that the whalers have thrown stun grenades at them, and tried to sabotage their boats.

- Vengeance -

Sea Shepherd USA and its renowned founder Paul Watson are now prevented by a legal injunction from leading whale defence campaigns against the Japanese.

But Cornelissen and Sea Shepherd Global, based in Amsterdam, have taken up the battle. They estimate that in the past 10 years they have saved some 5,000 whales from Japanese harpoons.

"The international community has failed to enforce the ICJ's rulings in the Southern Ocean, so it's once again up to Sea Shepherd to take action," the group says.

With Ocean Warrior leaving Amsterdam on Sunday to head to Melbourne, Sea Shepherd is readying to launch in December its 11th campaign in the Southern Ocean, dubbed Operation Nemesis.

Named after the Greek goddess of vengeance and justice, the conservationists hope this year the tide could turn in their favour.

"We've had campaigns where we've been following illegal whaling ships and because they had a superior speed, they could simply outrun us ... and we would lose valuable weeks during which they could chase whales," said the captain.

Now this warrior of the oceans, with its four engines can reach speeds of 55 kilometres an hour, around 25 knots, compared to its ocean enemies which only reach up to 20 knots.

"We asked for the biggest engines they had," smiled Cornelissen, shouting above the noise of the motors.

"I'm hopeful, because we've seen the whalers go down and they'll continue to go down, because we'll continue to make their lives miserable down there."