I like documentaries; this one is very well done and at the very least interesting. Despite some actions and ideas portrayed by the film-makers that I disagree with, I am sympathetic to the message.
More details here: http://www.thecovemovie.com/the_cove/synopsis.htm
The documentary brings attention to the underhanded practice of selling dolphin meat, contaminated with mercury, labeled as whale meat to the Japanese people. Markets only work with correct information; fraud is crime that should be stopped, not assisted by the Japanese government as shown in the film. I like to think that if the sellers of dolphin meat were forced to disclose such information, the market would solve the issue. This doesn’t even address the other moral question of killing sentient beings for food; do we eat monkeys or apes for food? But dolphins are ok, even though they reside on the same level of the food chain as we do?
Tangentially, there is also a reminder in the movie that trace amount of mercury are accumulating in the enviroment, and get concentrated in the top predators (Like people, dolphins, and whales). We (as in humans) really are slowly and diffusely killing ourselves and the rest of the planet with coal-fired power plants. (Note: I don’t have a proposed solution, nor do I advocate going to the extreme of shutting all coal power plants down. Coal is cheap, and cheap energy contributes to a higher standard of living. One balance is it worth it? I don’t really know, but I suspect not).