That depends on if that's what is really effective, but I'd be inclined to say no, since that would probably wipe out the whole crew.

Let me be clear: I don't think killing people for any cause is okay. But when it comes to damaging the ships in order to save the lives of the ENDANGERED whales, I'd file that under civil disobedience. Yes it's illegal - but I think it's still doing the right thing. If a species of whale is wiped out, it is an irreversible tragedy, not to mention it could have disastrous unforseen effects on the ecosystem it lives in.