Al Giddings was making his pitch to Brandon Tartikoff. He was throwing hard stuff to the president of NBC Entertainment, trying to make the network executive go for his offering.

The idea, said Giddings, a veteran underwater photographer with terrific credits, was to do an undersea documentary with a twist. Instead of giving the audience an hour of elegant underwater shots, why not try to get the audience involved too?

The idea was to get the viewers to develop some personal feelings about what they were watching. Specifically, let them see and vicariously experience an undersea adventure with all the attendant fears and thrills. As Giddings tells it, Tartikoff not only bought the idea, he asked for five hours instead of one. "He wanted sort of a 'Roots-Shogun' kind of experience," said Giddings.

The result of that network level pitch- and-catch is "oceanQuest," a five-hour mostly-undersea excursion, seen through the facemask of Shawn Weatherly, former Miss USA/Miss Universe and erstwhile adventuress. The series opens tonight at 8.

The original idea surfaced in talks between Giddings and Peter Guber, who co-produced with Jon Peters such films as "Missing," "Flashdance," "The Deep" and "Midnight Express."

Giddings, for 25 years an underwater photographer and diver, did the water work in "The Deep," the Bond flicks "For Your Eyes Only" and "Never Say Never Again," and the suffocating under-ice work in "Never Cry Wolf."

"Underwater work is really exciting, but I've been frustrated in trying to bring it to a network rather than PBS," said Giddings, with Jacques Cousteau clearly in mind. The problem, he said, is that people watch such a show without especially identifying with what they're seeing because the diving seems so far beyond their own ability.

"The idea grew to let the audience live these adventures through the eyes of a neophyte. We talked more and the idea of a young woman arose, and wouldn't it be something to get someone who'd done no deep diving? . . . Someone of really stout stuff who'd never been diving before."

At this point a difference of opinion bubbled up. Giddings was focusing on the "stout stuff" part of the job description. Maybe a woman like astronaut Sally Ride. Guber, with his Hollywood background, zeroed in on the "young woman" concept.

Giddings, who had worked with the likes of Jacqueline Bisset and Nick Nulty, was presented with prospect Weatherly. "None of the people I've worked with were as quick to learn as Shawn," said Giddings.

As part of her tryout for the part, Giddings had Weatherly suit up and tossed some weights to the bottom of a pool. Weathely retrieved them with the aplomb of a trained seal. Her performance in "the first 15 minutes," said Giddings, "that's how she got the job."

Getting the job and working at it for the year it took to film "oceanQuest" were two different things. "I was scared to death she might throw in the towel," said Giddings. "There were maybe a dozen times when I thought she might quit."

Like the time they dived among sharks; like the deep dive under the antarctic icecap, made through a small hole in the ice -- the only entrance and the only exit.

And there were other causes of anxiety that Giddings had not figured on. Weatherly got lonely during some of the periods when the "oceanQuest" crew was isolated. "Those were the times she couldn't make phone calls to her boy friend," recalled Giddings. "And she got upset when we ran out of fresh vegetables. I hadn't tapped my pencil over those problems at all. I had only worried about things like decompression."

In the end, though, she showed the stout stuff Giddings was after in the first place. "There'll be criticism that this film is trite," he said. "But there'll be no question of her fortitude."