“Chum” (**1/2 out of four) was a better-than-average horror thriller about a group of friends (Lisa Yaro, Alice Eve, Eric Michael Cole, and others) aboard a Mediterranean yacht who find that a ravenous shark is in the water and the psychotic yacht owner (Jim Klock) wants to sacrifice them. Yes, it’s another killer-shark movie that rips off “Jaws” (and also the James Bond film “Never Say Never Again”) but it’s proficiently made and as a bonus the shark looks genuinely vivid and scary. Yaro stands out in the cast and is especially winning.