Robert and Ruth Hallisy of Dayton, Ohio, backed their RV into its campground slot here, hooked up to the water and electricity, sat back and floated away.

      Literally.The Hallisys were in one of 59 recreational vehicles built for the road but now floating the waterways of middle America aboard one of the newest trends in tourism - river cruises on converted barges.

      "It sounded like a Tom Sawyer adventure to me," said Ruth Hallisy, eagerly waiting for the barges to depart one recently day.

      "I want to be Huck Finn," added her husband, Robert, to the amusement of fellow retirees waiting to board.

      This tour, the largest to date for the New Orleans companies that started them two years ago, is breaking new ground in the travel industry.

      Starting here on the Tennessee River, the 15-day cruise pushed north to the Ohio River, west to the Mississippi and then to New Orleans.

      Periodically, those aboard stop for off-shore tours, such as a barbecue at Loretta Lynn's ranch in Bucksnort, Tenn., a swing through Graceland and Beale Street in Memphis, trips to Vicksburg and Natchez and ultimately a party in the French Quarter.

      "It's kind of like sitting in a theater and watching the shoreline go by," says Bud Trembull of Little Torch Key, Fla., who was making a repeat trip. "There's no traffic. It's so peaceful."

      Indeed, the travelers, their cats and dogs can relax in their lawn chairs, chatting while watching the autumn leaves pass by on a wooded bank.

      The shore and river, ever changing, make each tour different. On occasion, says Trembull, they can glimpse deer, fowl and an abundance of other wildlife. When they're stopped, many set out fishing lines.

      Moreover, travelers are witness to the workings of the powerful river, its pilots and vessels, as well as the intricate locks that lift and lower boats.

      In part, the river cruises are modeled after similar cruises in Mexico in which RVs are loaded onto trains. This idea, though, came from the marriage of two companies.

      Eddie Conrad has an established boat-towing company in New Orleans, Compass Marine. When an avid RV enthusiast approached Conrad and suggested parking RVs on top of barges, Conrad thought it sounded feasible, though odd.

      Today, Creative World Travel - a New Orleans travel company that specializes in RV caravan tours - supplies the tour-seekers and Conrad's R.V. River Charters provides equipment and crew for the tour.

      "It's a full hook-up campground and exceptionally clean," says Wagon Master Ralph Sanders, a longtime RV caravan leader. Sanders and five other tour leaders tend to the campers' needs and provide games and entertainment.

      Conrad converted single-skinned oil barges (that now have largely been replaced by double-skinned barges) into floating campgrounds, 50 feet wide and 245 to 260 feet long.

      The barges used to carry their petroleum cargo inside. Now, their cargo is alive and on top, so the company reinforced supports beneath the decks, poured a foot-thick bed of concrete on deck to create a level parking lot, and built into each hull a 10,000-gallon freshwater container and another 10,000-gallon sewage water container.

      Then, for comfort, they installed electric and water hookups, a full kitchen, washers and dryers and safety precautions - such as a fence around the perimeter, life jackets and rafts and firefighting equipment.

      For the relief of dogs and cats aboard, each barge has about a 4-foot-square patch of sod.

      With about 16 feet between vehicles, campers have plenty of room to pull out awnings, hang colorful wind socks and lay out welcome mats.

      Two towboats power the trip to New Orleans by the Hallisys.

      Tour prices range from $945 to $4,490 and include the space for an RV, some meals and all the side-trips for two.

      The two companies offer eight cruises, including a three-day trip from Port Isabel to Corpus Christi, a nine-day cruise along the Tennessee River between Florence, Ala., and Chattanooga, and a popular 10-day cruise into the Cajun country bayous of south Louisiana.

      For information about RV barge cruises on the Mississippi, call Conrad's R.V. River Chaters at 800-256-6100. Each barge has full hookups and each RV has a 16 by 40 foot slot. Prices range from $945 to $4,600.