Movies opening Friday:

"16 Blocks": A troubled New York cop (Bruce Willis) must escort a happy-go-lucky crook (Mos Def) from jail to court, but dangerous forces are out to stop them. Helmed by "Lethal Weapon" director Richard Donner. (PG-13)

"Aquamarine": Based on Alice Hoffman's popular children's book, the story tells of two teenage girls who discover a mermaid living in a swimming pool at their neighborhood beach club. When the mermaid develops a crush on the club's lifeguard, the girls plot to return her to sea to save her life. Stars Emma Roberts (Julia's niece), Joanna Levesque and Sara Paxton. (PG)

"Dave Chappelle's Block Party": Back in the spotlight after a self-imposed hiatus, the popular comic presents his dream concert lineup (including Kanye West, Mos Def, Erykah Badu, the Roots, Jill Scott, Dead Prez and a reunited Fugees) and puts on a big ol' outdoor party in Brooklyn, N.Y. Director Michel Gondry ("Eternal Sunshine of the Spotless Mind") documents the concert and the jubilant road trip that led up to it. (R)

"Ultraviolet": Babelicious action star Milla Jovovich stars in this futuristic action flick as a genetically altered woman with martial arts skills and chameleon-like abilities trying to protect a boy from a government out to kill him. (PG-13)