“Whale Wars” (8 p.m., Animal Planet) embarks on its third season with two new vessels, a more confrontational attitude and plenty of high-risk behavior on the high seas. Make that the high seas near Antarctica.

As fans of this documentary series already know, the Sea Shepherd group is dedicated to stopping Japanese whaling vessels from their mission. Over the years, the volunteers have begun to fear that the Japanese military has been trailing them and reporting their position to the whaling fleets.

This season, the Shepherds’ new high-speed boat, the Ady Gil, sets out to get between whalers’ harpoons and their prey. “Whale Wars” treads some strange waters. Like any reality series, it’s dependent on suspense. But some of the Ady Gil’s travails have already been reported on extensively in the news.

I won’t give too much away here, but both sides have developed an in-your-face attitude, resulting in many brushes with injury, near death, property destruction and legal complications. It doesn’t matter how much you care about saving the whales or animal rights, “Whale Wars” is riveting stuff, at times closer to a kind of war footage than the usual reality fluff.

• New episodes of the Canadian series “Flashpoint” (8 p.m., CBS) return without a great deal of fanfare. It stars the always capable Enrico Colantoni as the head of a police tactical unit called in for extreme cases. Tonight: a terror group distributes bombs throughout the city.

• Now in its fourth season, “Friday Night Lights” (7 p.m., NBC) continues to receive rapturous reviews and has cultivated a cult following despite anemic ratings. Fans of “Lights” should be happy to know that the series will air in its entirety on ABC Family beginning in fall 2010.

• How do you spell “tradition”? Chris Harrison hosts the final rounds of “The 2010 Scripps National Spelling Bee” (7 p.m., ABC). This marks the culmination of a contest featuring 273 champion spellers, ranging in ages from 8 to 15, who have qualified by winning local competitions. Fans can also catch the semifinals earlier in the day (9 a.m., ESPN).

• “Fox Legacy with Tom Rothman” (7 p.m., Fox Movie Channel) looks back at the iconic 1969 romantic Western “Butch Cassidy and the Sundance Kid,” starring Paul Newman and Robert Redford. The retrospective includes an interview with former movie executive Richard Zanuck.

Tonight’s other highlights

• Memories of Devalos’s late daughter haunt him on “Medium” (7 p.m., CBS).

• Matt calls on old friends for support on “Friday Night Lights” (7 p.m., NBC).

• An accusation drives an office worker off the deep end on “Past Life” (7 p.m., Fox).

• Director Brian DePalma channels Alfred Hitchcock in the 1980 thriller “Dressed to Kill” (7:45 p.m., IFC), starring Angie Dickinson and Michael Caine.

• A fellow physician needs help on “House” (8 p.m., Fox).

• Telford divulges a threat to the Destiny on “Stargate Universe” (8 p.m., Syfy).

• A romantic gesture offers a new opportunity to return to Essex on “Gavin and Stacy” (8 p.m., BBC America).

• A hurricane fills the wards with interesting stories on “Miami Medical” (9 p.m., CBS).

• Merlin finds a fetching druid in distress on “Merlin” (9 p.m., Syfy).

• Office politics dominate the company picnic on “Party Down” (9 p.m., Starz).