Montreal — You stand on the banks of the St. Lawrence River, not far from downtown Montreal, and stare with awe at the very reason for this city's existence - the foaming, thunderous fury of the Lachine Rapids.
At this juncture, where the river narrows to a mere half mile, and the pace of the water quickens appreciably, there are thousands of standing waves, some of them 15 feet high, a dozen or more whirlpools, and two hydraulics - depressions, or valleys surrounded by towering walls of water, caused by the backlash of rushing waters.
When Jacques Cartier, the French explorer, arrived here in 1535, his ships could go no farther. The mighty river and the massive Lake Ontario, which offered such easy navigation to the interior, and perhaps even the fabled Northwest Passage, lay tantalizingly close but unavailable to all shipping from the east. This is where goods had to be offloaded, portaged upstream, and reloaded onto ships that would be built above the thundering Lachines. So the settlement that became Montreal began here because of the need to portage.
At the time, Indians in birch-bark canoes would joust with the rapids in a ride that rivaled for thrills the best of the roller-coaster rides at a theme park. The first Frenchman to take the ride was drowned, along with the Indians who took him. The next day, Samuel de Champlain took the trip and survived, saying in his journal: ''Only the Indians have the audacity to do such a thing.'' Today you can include with the Indians two sons of a Polish millworker from Pittsburgh.
Joe and Jack Kowalski, who rode the rapids countless times in a high-powered jetboat, now take others with them, for a $25 fee. It's the latest attraction in town, and when you bounce, bob, dart, and slide through the thundering torrent that surrounds you, your admiration for the Indians reaches new heights. For that matter, you're pretty impressed with the Kowalskis, too.
Back in 1975 the Kowalskis began running wilderness tours, a long rubber-raft adventure down the foaming Ottawa River. That first year they attracted 75 customers; last year 4,500 took the thunderous ride. Then a few years later someone suggested the brothers might take a look at the Lachine Rapids. They did , taking a good hard look at them from both sides of the river and from a helicopter hovering low over the rushing waters.
What they saw impressed them. The Lachines were all they had been told they were and more. ''Awesome,'' was the Kowalski assessment. Moreover, the rapids were virtually on downtown Montreal's doorstep. No other major city anywhere had this river-ride opportunity. Unlike other river adventures, their own on the Ottawa River included, a tourist could ride the Lachines, be thrown about in a manner not even Disney World can duplicate, and then take in a leisurely dinner at a superb restaurant or perhaps a theater in downtown Montreal an hour or so later.
But there was one major drawback. The Lachines are half a mile wide at this point but only a few hundred yards long. The time-honored way of placing people in a rubber boat would result in an all-too-brief period of excitement, and then it would be plain sailing. In fact, as far back as 1840 much larger boats with skillful skippers at the helm would sail over the rapids to provide travelers to Montreal from much farther upstream a few moments to write home about just before they docked.
The answer for the Kowalskis, then, was some sort of powerboat ride in which tourists could joust with the Lachines repeatedly at varying points across its half-mile width. And that is exactly what happens.
''Gentlemen, we have the technology,'' the Kowalskis said, borrowing a phrase from a well-known TV production, and they promptly had a special flat-bottomed aluminum jet boat built and tested. Now, two such boats take tourists on the ride. In a matter of minutes the 700-horsepower jets whip you from downtown Montreal to the Lachines, riding up through ''paths'' in the rapids known only to the pilots themselves. Then, with the motor on idle, the boat is turned adrift to ride and bounce through the rapids like a floating tub.
It's an incredible experience and a very wet one, particularly if you ride up front, as I did. We were all decked out like the Gloucester fisherman in the most storm-resistant gear. But it is not enough to keep the front-seat participants dry, for the waves break over the bow and envelop you. A few seats back and you still get wet, but not drenched.
The Kowalskis are unabashed about their new adventure. ''The best thing to hit Montreal since the Olympic Games,'' is how they put it.
Not all tourists will necessarily agree, but all will know that they have had one whale of an experience.
The Lachine rides take place every two hours, seven days a week, between May 20 and Labor Day (Sept. 4) and on weekends only in September and October, other than for specially chartered rides. The cost is $25 per adult and $20 for child. Wear old clothes. You will get wet, even though rain gear is provided. For information write to Lachine Rapids Tours, 105 Rue de la Commune, Montreal, H2Y 2C7. Phone (514) 284-9607.