TURN-ONS AND TURN-OFFS IN CURRENT HOME ENTERTAINMENT RELEASES : Excellent Good Fair Poor : VIDEOCASSETTES

“Secrets of the Titanic.” National Geographic/Vestron. $29.95. One of the most anticipated video events of the year, since it’s debuting this week on cassette before being seen anywhere else, this documentary turns out to be terrific. Most of the tape is devoted to an account of the search for the Titanic, lying two miles under the ocean, and to eerie, spectacular underwater footage of the wreckage--scanned by a robot submarine with a TV camera. The tape, narrated by Martin Sheen, begins with an absorbing history of the supposedly unsinkable ocean liner, which went down on its maiden voyage 74 years ago, killing more than 1,500 people. At the end of the video is a stunning re-creation of the ship’s final hours. There’s only one problem with this documentary: At one hour, it’s too short. Information: (203) 968-0000.