Watson, founder of the Sea Shepherd conservation group, was detained Saturday in Frankfurt on a warrant issued by Costa Rica, the activist group said in a release.
Sea Shepherd said the 2002 incident occurred in Guatemalan waters when Sea Shepherd encountered an illegal shark-finning operation, run by a Costa Rican ship called the Varadero. The crew of the Varadero accused Watson of trying to kill them. Watson denies the allegation, Sea Shepherd said.
He is being held in Germany pending extradition to Costa Rica.
Pregnant Mila Kunis wins 'Best Villain' at MTV Movie Awards
'Happy' fan videos make Pharrell cry [VIDEO]