Standing on the bow of the Gator Gal, advertised as the world's largest airboat, Forrest E. Orebaugh knew exactly what his passengers wanted. They wanted to see alligators and lots of them.

"I can't guarantee it," he said, as the 70-foot vessel bobbed next to the dock. "Every trip is different. We don't have fences here, and we don't keep animals in cages. What you see is wild. But we should see some alligators."People who travel with Orebaugh, or one of his colleagues, seldom go home disappointed. Seven days a week, as many as six times a day, the Gator Gal tours the lake here at Myakka River State Park, the 29,000-acre wilderness east of Sarasota.

The lake is a birdwatching paradise, and its banks are sometimes the grazing grounds of deer and wild hogs, but alligators are both plentiful and the main attraction.

Native Floridians may regard the big lizards as something of a swimming cliche, but for many tourists or people who seldom escape the city, animals with big teeth represent the state at its most exotic and primitive.

"The only rules on our tour are please don't smoke and please don't stand," Orebaugh said as he shoved the airboat into the water.

Nobody had a problem with the no-smoking rule. But the first time an alligator showed its snout, several passengers jumped to their feet, snapped furious photographs and shouted with excitement in several languages. The Gator Gal was jammed with visitors from Canada, Germany, and Italy as well as states north of the Mason-Dixon line.

"My first alligator!" said Mildred Rogon of Detroit.

"I'll bet it could do damage with those teeth!" shouted her husband, Jim.

Orebaugh, 58, dressed from head to toe in safari-inspired khaki, understood their enthusiasm. Alligators are somewhat of a novelty to him, too. He was raised on an Ohio farm and worked in the Cincinnati school system until his retirement to Florida in 1986. A former biology teacher who has always been interested in natural history, he joined the Gator Gal staff four years ago.

Sandhill cranes thrill him. So do great blue herons, ospreys and bald eagles. He sees those on his tours, and venomous cottonmouth water moccasins, garfish and pie-sized turtles. But a good alligator gets his juices flowing.

"We saw a 15-footer yesterday," he said, and the announcement was greeted by gasps. "The biggest alligator on record was 19 feet, two inches, from Louisiana. Some of our alligators here weigh more than 1, 000 pounds."

Orebaugh is more than a naturalist. He collects the fares ($6 for adults; $3 for children 6 through 12), does the boat's mechanical work and then lterally puts on his captain's hat. He switched on the engine, pointed the boat toward the lake and began lecturing through the microphone that allows him to be heard over the engine's roar.

Lecturing aboard the Gator Gal comes naturally to Orebaugh. It's just like teaching, he tells people, and without the discipline problems and the need to assign homework. He explains ecology simply and in a friendly way that suggests Mister Rogers talking to adults.

"That's a little blue heron," he said, gesturing at the small wading bird. "What do little blue herons eat? Little blue herons eat frogs and minnows for the most part. That's the little blue heron."

The little blue was sharing the bank with a 4-foot-high great blue heron, which stood on one leg.

"Great blue herons eat fish," the tour guide said. "They also eat a lot of snakes. And when alligators hatch during the summer, they'll eat baby alligators."

When you travel with Forrest Orebaugh, the subject sooner or later gets back to alligators and the food chain. A wilderness lake such as Myakka is more or less a great big delicatessen. Baby alligators that manage to survive hungry herons and garfish eventually put on bibs and return the favor.

"When alligators get big, they eat a lot of great blue herons," Orebaugh said.

Alligators devour more than herons of Myakka Lake. Gator Gal passengers over the years have watched as alligators made meals of turtles, snakes and even deer who came to drink out of the lake. Orebaugh saw a gator grab a Dalmatian dog that a park visitor had allowed to go for a swim.

"For a lot of people, it's shocking to see something like that," he said. "They don't realize that the natural process is for higher animal life to feed on lower life. And alligators are at the top of the food chain."

Five sandhill cranes, taller than any dining room table, fed contentedly in the shallows as the Gator Gal continued. Three more flew in a "V" overhead and talked to each other in voices that sounded like rusty gates. There were wood storks and white ibis and tri-colored herons. Orebaugh pointed out moorhens and anhingas. A big alligator - it must have measured 10 feet - cruised across the lake.

"They can swim 15 to 20 mph," he said. "They can swim faster than any human could ever hope to swim. If one was ever to come after you in the water, you'd have to do something other than try to out-swim it."

"What would you recommend?" asked a woman, sounding overly concerned.

"I wouldn't go in the water where I know there are alligators."

At least 500 alligators, and possibly as many as 1,000, live in Myakka Lake, Orebaugh told her. On warm weekends, the lake is also a favorite fishing hole for anglers, who wade among the alligators. Orebaugh's passengers gasped at that fact. He let them think about it, and then told them that there has never been an attack on a human in the state park.

"I don't think alligators look at humans as a food - in the daytime. But the rule of the night is different. Alligators recognize two things at night: other alligators and food. Most alligator attacks on people happen at night."

The sun was happily overhead when Orebaugh turned the Gator Gal around and headed in. On the way he gave the natural history of water hyacinths, and explained that tannic acid from vegetation was what caused the water to be dark.

"And over there," he said, pointing to a tree whose limbs were heavy with large, black birds, "are our vultures. They're hoping for an unfortunate landing, but we're going to disappoint them."

Orebaugh landed the Gator Gal gently. If the vultures were disappointed, they never let on.