“Snowfall” season finale, 10 p.m., FX, rerunning at 11. Some fierce collisions have been propelled by two things: A reporter (tipped by Franklin’s father) wrote about Teddy’s CIA guns-for-drugs scheme; also, Leon accidentally killed the niece of Manboy, a rival gang boss. Last week, Teddy killed the reporter after a car crash; Franklin killed Manboy and his gang. Here are the aftershocks, some quiet and some not. This would be a great series finale, but “Snowfall” will return.
“Nature: Sharks of Hawaii,” 8 p.m., PBS. On Thursday, TV will celebrate Earth Day with a splendid surge of nature films. While we’re waiting, we can catch this excellent one. It focuses partly on Hawaii’s thriving sharks but also detours into other intriguing underwater views.