The waters haven't been kind to American Classic Voyages (AMCV): In the past three years, the river-cruise line has drifted into the red. But its stock, which dipped to 9 from a high of 12 5/8 in February, has made a comeback: It closed above 11 on Aug. 5. What's up?

One big stakeholder who has been a steady buyer despite the losses is Chairman Sam Zell, a real estate mogul and financier. Equity-DQSB--a group that includes Zell and American Classic directors Arthur Greenberg, Ann Lurie, and Sheli Rosenberg--holds 51% of the stock. The curious thing is that, on July 31, the board authorized repurchase of 1 million shares on the open market or in negotiated transactions. American Classic has 13.9 million shares outstanding.

Some pros believe Zell is preparing to take the company private in a leveraged buyout. ''American Classic is an attractive target for larger cruise-line companies,'' says one money manager who has been snapping up shares. ''In the past two weeks, more market makers have come into the stock, suggesting a surge of new interest,'' says one trader.

American Classic has three paddle-wheel steamers that cruise the Mississippi. One of its ships, the Delta Queen, is a National Historic Landmark. Another ship, the Mississippi Queen, carries 416 passengers, and its newest vessel, the American Queen, has a capacity of 436 passengers. American Classic also owns the 582-foot Independence, which cruises the Hawaiian islands.