The Sea Shepherds depart on their 2010/2011 ant-whaling campaign with a new, fast interceptor vessel. Early on, they find two harpoon ships before the whaling fleet has killed a single whale. Could they be set up for their most successful campaign ever?

After engaging the harpoon ships using the small boat teams, Captain Paul Watson makes the call to abandon the harpoon ships and go in search of the factory vessel. After a few hours of sailing, the tables have turned — two harpoon ships begin tailing Sea Shepherd!

Tailed by a harpoon ship, the Steve Irwin enlists the help of the Sea Shepherds' new, fast interceptor ship in an attempt to break free. Meanwhile, the Bob Barker crew spots a large blip on their radar and believe it could be their ultimate target: the Nisshin Maru.

When damage happens to one of the small boats, and the Bob Barker is five hours away, the crew realizes that they will have to spend a night at sea. But the crew is wet and freezing already, and early symptoms of hypothermia begin to set in.

The Bob Barker desperately searches for their two small boat crews who were lost at sea in the aftermath of a daring mission. Meanwhile, the Gojira locates the whalers' refueling vessel and Locky plays a dangerous game of "chicken" with the massive ship.

New Zealand's Navy contacts the Steve Irwin to respond to an emergency distress signal where five crew members from a Norwegian sailboat have gone missing. Now the Sea Shepherds must risk their lives in a dangerous mission to find the missing mariners.

As the first leg of their campaign comes to a close, the Sea Shepherds battle physical and mental exhaustion, especially pilot Chris Aultman. Thanks to an anonymous tip, the Steve Irwin finally locates the whalers' factory ship, the Nisshin Maru.

The Bob Barker and Gojira launch an ambitious assault on the harpoon ship that has been following them and manage to completely disable the whaling vessel. Now free of its tail, the Barker continues searching for their ultimate target, the Nisshin Maru.

The Sea Shepherds finally locate the factory vessel after months of searching, but it promptly tries to evade the Gojira.

In the fourth-season finale, Watson claims a major victory after 30 years of fighting, while he and the crew reaffirm their commitment to stopping the whaling fleet.