TONIGHT’S BEST BETS

Finding Your Roots

(2) WGBH (11) WENH 8:00 p.m. Henry Louis Gates, Jr. helps actor John Lithgow and journalist Maria Hinojosa to trace their roots in this new episode. Each of the notables learns that they come from a line of successful people who lived in the U.S. before the country was founded.

Pooch Perfect

(5) WCVB (9) WMUR 8:00 p.m. Australian actor and comedian Rebel-Wilson hosts another episode of this fun competition series in which dog stylists show their proverbial chops throughout a series of challenges in order to win the glory and cash prize as champion of the show.

47 Meters Down

SYFY 9:00 p.m.

While vacationing in Mexico to help her sister (Mandy Moore) get over a recent break-up, Kate (Claire Holt) plans a cage dive to see some sharks. But when the winch snaps and the cage begins sinking, the sisters find themselves underwater.