BOOK REVIEW : Undersea Story: Shallow but Fun : TO KILL THE LEOPARD <i> by Theodore Taylor</i> ; Harcourt Brace Jovanovich $21.95, 324 pages

“To Kill the Leopard” is a curiously old-fashioned war novel. Unlike the U-boats that figure so prominently in the story, the book itself does not dive very deep or take much evasive action. In a sense, it’s “Das Boot” Lite.

Theodore Taylor, an award-winning author of mysteries for young readers, tries his hand at adult fiction for the first time in “To Kill the Leopard,” and he manages to come up with a fast read that will appeal to war buffs. But the book does not have much to offer the reader who is not fascinated with the finer points of submarine warfare.

Traces of “Moby Dick” can be detected in the plot. Sullivan (Sully) Jordan is an American merchant seaman who lands in the drink--not once but twice--because his ship has been torpedoed by the same relentless Nazi submarine with a snarling leopard painted on its conning tower. And so Sully sets out to avenge himself on his tormentor.

“You saw the sub again?” asks Sully’s wife when he describes a recurring nightmare about the torpedo attack.

“That damn leopard was chasing me,” says Sully, telegraphing the final show-down that ultimately brings the book to a big finish.

Sully’s adversary is the commander of the leopard sub, a handsome young officer named Kammerer who gives Tarzan yells and beats on his chest whenever he sinks a ship. He’s as “Teutonic as the Brandenburg Gate,” as Taylor puts it, but his mother was French and he has a preference for French cuisine and French woman. As if to let us know that Kammerer is no barbarian, Taylor depicts him as a sophisticated reader of Henry Miller, and Kammerer machine-guns a lifeboat only when one of the survivors takes a shot at one of his officers.

But Kammerer is a risk-taker, a cowboy at sea and he even reads Zane Grey novels as he goes into battle. In fact, he so craves the medals that Hitler hands out to successful U-boat commanders--the Nazi equivalent of carving notches on a six-gun--that he takes one risk too many in the encounter that turns into the nautical equivalent of the shoot-out in “High Noon.”

Taylor weaves a few subplots into his otherwise straightforward narrative. For example, Kammerer’s eye falls on a pretty young Frenchwoman, who has been encouraged by the Resistance to seduce a U-boat captain to gather intelligence: “You’re very pretty and quite sexual,” says her contact in the underground, a cloistered nun who makes sure that the young woman has mastered the techniques of birth control before bedding down her Nazi lover.

Taylor’s narrative style consists of short scenes that flash between Allied convoys, Nazi wolf packs, French Resistance fighters, British psychological warfare specialists and the home front. He never slows down or digs in, but, at the same time, he never falters in driving his story forward to its climax on the high seas.

Along the way, Taylor shows off what he learned in his archival research into submarine warfare during World War II. What I liked best, in fact, were the asides that allow us to understand what it was really like to serve aboard a stalking U-boat or the merchantmen that were its prey.

Sheer avoirdupois, as we learn, was a crucial factor in a crash dive, and the crew of the submarine would rush to the bow to ensure a faster descent. The stretch of ocean beyond the range of Allied aircraft was called the “air gap” by the Allies and “the death hole” by the Nazis. And the convoys, which offered at least some faint hope of defense and rescue during a submarine attack, were confined to ships that were able to make at least seven knots.

“Clunkers that couldn’t make seven,” Taylor explains, “were considered expendable and sailed alone, often doomed.”

Now and then, Taylor comes up with dialogue that sometimes soars to metaphorical excess and sometimes thuds to the ground. “Wireless is our rope to spy heaven,” says one British sub watcher. And then, a few pages later, the author burdens his characters with a conversation designed to explain why an empty oil tanker will blow up if a torpedo hits it.

“You know what a flash point is?” Sully asks a crew mate.

“Not really.”

“It’s the temperature at which vapors form a flammable mixture with air.”

“To Kill the Leopard” plays it so safe and stays so firmly within the familiar genre of the World War II thriller that we are never truly surprised by what happens. But the book caught and held my attention, and by the time we see Sully packing his cross-bow for the fateful voyage aboard a “Q-ship” in search of the leopard-sub, I was hooked.