There always will be governments and corporate entities who want to keep their operations secret, because exposure of their illegal or immoral behavior would shock the world into action against them.

Two fascinating new documentaries, "The Cove" and "Burma VJ," tell of the risky and heroic efforts to expose two horrific secrets -- a dolphin slaughter in a Japanese village and the oppression of citizens in Burma -- and the dangerous extremes to which the powers that be will go to stop them.

"The Cove" is an activist thriller -- part caper flick, part environmental cry to the world -- that will set your heart racing, while breaking your heart at the same time. It aims to reveal what happens every September in the coastal Japanese town of Taiji, where thousands of migrating dolphins are lured into a cove. Some are taken to be sold to aquarium shows, for prices up to $150,000 each.

To Ric O'Barry, a former dolphin trainer who has become a vocal opponent of keeping dolphins in captivity, the trading of these intelligent and gentle creatures is a travesty. It's also a practice that fills him with guilt, because he trained the stars of the '60s TV series "Flipper" -- and he feels personally responsible for launching an industry he now abhors.

But what happens to the dolphins in Taiji that don't get sold for aquarium shows is even more horrifying. The dolphins, some 23,000 of them a year, are systematically slaughtered and cut up for meat -- which is sold in Japanese supermarkets, usually mislabeled as whale meat, and laden with toxic levels of mercury.

O'Barry and Louie Psihoyos, the co-founder of the Oceanic Preservation Society and the film's director, know what's going on in Taiji. What they don't know is how to prove it. Outsiders are viewed with suspicion, anyone with a video camera is harassed by fishermen, and anyone caught trespassing is arrested.

That challenge takes up the central part of "The Cove" and delivers the movie's thrills and humor. Psihoyos assembles a crew, a crusading "Ocean's 11" team, to figure out how to get cameras into the cove and bring back the video evidence.

A similar sort of "Mission: Impossible" plotting is at the heart of "Burma VJ," which tells of a group of videographers trying to show the world what's happening in their southeast Asian nation.

Dissent is quickly stifled in Burma. A solitary protester may hold up a sign in downtown Rangoon, and within two minutes that person is surrounded by plainclothes cops and shoved into a car bound for who-knows-where. Since student protests were brutally quashed in 1988, killing 3,000 people, the military rules by fear.

In August and September 2007, something started stirring, though. Burma's Buddhist monks, the one group whose power rivaled the military's, began to march en masse in Rangoon and other cities. Video of those protests was shot by a loose network of underground journalists and smuggled out of the country to be broadcast on an Internet TV station based in Oslo, Democratic Voice of Burma (DVB) -- and that video was quickly picked up by the BBC, CNN and other global outlets.

Danish director Anders Østergaard constructs a narrative for these events around "Joshua" (not his real name), a videographer who shot some footage of protesters -- until his cover is nearly blown and he retreats to Thailand to be a sort of assignment editor, guiding DVB's camera operators and getting the footage of the military's oppression.

There's entertainment value in both documentaries, though "The Cove" moves more fluidly like a crackling thriller. But in both films, what makes the movie experience worthwhile is the gut-punch of the footage their crews have collected, which exposes nasty secrets and shows us viewers what we can do to end the violence we've just seen.

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