"The Deep," opening today at nine area theaters, is a reasonably proficient and entertaining movie version of Peter Benchley's best-selling adventure novel about treasure-diving off Bermuda. Since Benchley's previous opus was "Jaws," which was transformed by director Steven Spielberg and several inspired collaborators into a streamlined sensation, similar excitement from "The Deep." In a word, don't.

"The Deep" has marvelous underwater sequences - in fact, it's a much classier operations whenever the company submerges - and it generates a certain amount of tension, but it's not an overwhelming sort of thriller. Supervised by Peter Yates, a competent methodical director, "The Deep" is as good as it needs to be for relatively undemanding summetime diversion.

Although "The Deep" was a better-written book than "Jaws" and even seemed more tailor-make for movie adaptaion, the improvement isn't evident in the film. Benchley evidently worked on the first draft of the screenplay, but his influence seems to have been obscured by less sophisticated storytellers.

The casting is a little disillusioning. One didn't really expect Robert Shaw to embody the towering, powerful island recluse, Romer Treece, but he seems less commanding than one hoped. While remains the most distinctive actor in the case, Shaw was a larger-than-life presence in "Jaws." With the exception of Jacqueline Bisset, who looks wonderfully desirable as the heroine, there's been a general shrinkage and slippage in character dimension from book to screen. Quite the opposite happened in "Jaws" Nic Nolta looks like a bank in the stills for "The Deep," but he acts like a barely articulate lunk in the movie. Nolte utterly fails to suggest the intellect motivating this middle-class danger-seeker, probably a Bencley self-portrait. He's just a Viking warrior in scube drag.

Nolta and Bisset, are a vocationing couple who stumble upon two layers of treasury while diving for sport. Cartons of morphine ampules from a sunken World War II ship are found resting among trinkets that date from the early 18th century and may be worth a king's ransom. A local underworld figure played by Louis Gossett tries to get his hands on the drugs, first soft-soaping and intimidating the visitors, who discover a confederate and protector in the Shaw character. The heroes endeavor to outfox Gossett and his henchmen until they can collect some verifibly valuable trinkets and scuttle the drugs.

The good guys and bed guys line up along racial lines that seemed vaguely disquieting in the book and downright embarrassing on the screen, where the human abstractions are embodied by actors. It's not that one objects to blacks playing the villains per so. The filmmakers end up catering to a good deal of simpleminded fantasy on both sides of the color linew by placing Bisset in frequent danger of inerrocial rape. It's a take-out, and since Bissett's bosom has been the main photogenic attraction to the first 15 minutes of the movie, it's quite hypoctitical to single out the black characters for getting lustful action.

Benchley wrote up a suspenseful momentum in the book while shifting from underwater to topside episodes. The film sustains tensions and achieves a distinctive mood only underwater. I've never seen sharper deep-sea cinematography, and each new dive brings some fresh element of peril and unexpected visual bonus, such as the flashing strobe when Nolte tries to escape a meray eel and loses his underwater camera or the magical appearances of the ampules as they're uncovered and dance lasily in the silt and water. [PARAGRAPHS ILLEGIBLE]