Water beds, their initial market splash long over, are racking up solid sales

Mike and Sharon Rose of Columbus, Ohio, have been water bed fans for 10 years. In fact, they like them so much, when their new baby arrives next month they plan to start him out on a water crib.

The baby will join the fast growing number of people who literally drift off to sleep.

Charlie Hall, a design student in California in the '60s, came up with the not-terribly-well-remembered ''Jell-O couch.'' That evolved into the faddish water bed, and that has become big business over the last decade. Water beds now make up the most rapidly growing sector of the home furnishings market.

A fad no more, ''water beds are becoming a well-accepted general consumer product,'' says John McNeill, president of the Waterbed Manufacturers Association. ''It is now the No. 2 choice for bedding in the United States.''

In 1981 water bed sales surged to almost $1.3 billion, accounting for 10 to 12 percent of the bedding market. Through most of the '70s, sales grew at about 25 percent. And even in 1982, a slow year, the water bed industry grew at a rate of 12 percent.

Several factors contribute to this rising tide of popularity - low cost, comfort, even body support and weight distribution, and what many people see as health benefits.

Through the '60s the fledgling industry was a little wet behind the ears and slow to get started. But as the beds gained popularity and sales picked up, ''business skills and a capital base were added to run it as a viable business and a major venture in home furnishings,'' Mr. McNeill says.

Although recently a number of the nation's 3,000 water bed specialty stores have found the waters too deep and have gone under, many conventional furniture stores and department stores like Sears, Roebuck, J. C. Penney, and Montgomery Ward have picked up the product.

McNeill says he thinks a large number of the country's 24,000 furniture stores will soon sell water beds. He sees tremendous potential in this trend saying, ''Our No. 2 position (in the market) came with relatively limited availability.''

Water beds can be very inexpensive. Prices range from $99 to more than $1,000 . According to Dorothy Fraser, sales manager at the Boston Bedroom!, ''a complete water bed is not any more expensive than a good-quality mattress and box spring.''

Despite the growing popularity of their product, water bed merchants find they still have some misconceptions to contend with. ''For instance, water beds are not too heavy, they never have been,'' Ms. Fraser says. And Mr. McNeill adds , ''There has never been a case of a water bed going through a floor.''

Also, fewer than 1 percent of water beds ever leak, and all water beds include a vinyl safety liner to contain lost water, he says.