It is the name of the vessel used by Paul Watson and his crew often in dangerous waters such as those near Antarctica for the sole purpose of disrupting the on-going large scale slaughter of numerous whale species. Watson, the captain and leader, is clearly a highly flawed man. Egocentricity is likely one of those flaws, among many others. But even that is closely allied to his extreme dedication to his cause, his fearlessness, perseverance, and his willingness to take risks most others would shrink from, in order to make a real difference. The potential murder of most if not all whale species to the point of extinction, would not only be a great crime, but a permanent stain on the entire human species. The real point is that the sea shepard was engaged in activities that in a sane, ethically functioning world would have been carried out by the proper authorities. In the gaping vacuum left by indifference and inaction, Paul Watson dared to step in. Although true that it would be foolish to be pro-vigilante as such. I think it depends. My sense is that in 5o years time (or less) Mr. Watson, that flawed, obsessed, aggressive activist, who no doubt strayed off the reservation of more acceptable protest, will be utterly vindicated and the whalers grandchildren more or less ashamed - even though it's their governments and industry bosses that are really to blame. Bottom line, Paul Walker saved a shit load of whales. That's good enough in my book.
I highly recommend the documentary Eco-Pirate, the Story of Paul Watson, which includes the adventures of the sea shephard. It not only covers a lot of ground in terms of modern history, giving context to Paul's struggles and passion as well as to the founding and early days of Greenpeace, but also gives a fair, that is both sympathetic and critical, overview of the man's life. Only if one was dead set against the subject of the film with something of a prejudicial distaste already in your mouth, might I say this movie's not for you. On the other hand if you give the slightest crap about marine life, conservation or the dilemmas facing committed activists then definitely check it out.