Actor Adrian Grenier's character in "Entourage" is an actor called Vincent Chase — and in that HBO series, Vincent takes on the role of Aquaman in a film. Now, Adrian himself's become Aquaman — for an Oceana PSA.

In the short video, Adrian swims with endangered bluefin tuna, pointing out that while the fish are powerful swimmers, they're still not powerful enough to escape the fishing nets — and are quickly disappearing.

To join Aquaman's call to help save bluefin before they're gone, visit Oceana's site to sign a petition calling on Congress to protect bluefin. And for an overview of why bluefin are faring so badly, read Paul Greenberg's in-depth article in the New York Times, "Tuna’s End."

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Adrian Grenier, the eco-Aquaman
The 'Entourage' star swims with endangered bluefin tuna for Oceana.