Fear the Enviro-Pirates
I had never heard of the Sea Shepherd conservation society and was pretty incredulous when I was pointed to their history. They sound like a super-hardcore version of Greenpeace, and indeed they were founded as a splinter group of Greenpeace.
One of the most hardcore parts of their story, additionally interesting for showing that radical environmentalists are not all Commies, was when they bombed the Soviet spy ship with paint and threatening messages. Bombed, from a plane. Generally lots of naval warfare and trouble with authorities.