I’m not quite sure what Johnny Depp is doing in this pirate yarn, but it works. As Captain Jack Sparrow, a ramshackle scamp with dirty dreadlocks and enough eye makeup to incite jealousy in a sixth-grade girl, he speaks in an accent that’s slightly British but mostly slurred. Turns out his loose-cannon act is the best approach for an adventure film that at its best recalls the daffy delights of The Princess Bride.