WASHINGTON (Dow Jones/AP) ? If a rising tide lifts all boats, then the marine shipping industry is certainly benefiting from a confluence of high demand for its services and a swelling initial public offering market.

The marine transportation industry hasn?t traditionally been the stuff that IPO dreams are made of, being populated by cyclical, old economy companies that schlep large quantities of heavy materials from one end of the globe to the other.

From 1990 to 1993, the industry averaged just one IPO a year, according to data from Thomson Financial. But in the past two weeks, three carriers ? Diana Shipping Inc., Horizon Lines Inc., and TBS International Ltd. ? have filed to go public following the successful offer of DryShips Inc. in February. Last year, five marine transport companies came public.

?It is unusual. These are the kind of companies you don?t see hit the market too often,? says Tom Taulli, co-founder of Currentofferings.com, a Web site that tracks IPOs. ?But the IPO market is not just about tech anymore. It?s become much broader.?

The pace of IPOs so far this year has been better than at any time since 2000, and the types of companies coming to market have included everything from florists to decades-old chemical producers, so the marine transport industry isn?t the only old-line sector launching itself at public investors. As with any string of related IPOs, all it takes is one company to tap the public markets successfully, and competitors will follow.

That was the case with the leading marine transport IPO launched this year by DryShips, a Greek shipper that went public at $18 a share in February and closed up 12 percent its first day. Its shares fell 13 cents to $20 Monday morning on the Nasdaq Stock Market.

Last year, five marine transport companies that specialised in petroleum product shipping hit the public market, capitalising on demand for oil shipments.

This year, the trend is leaning towards companies like DryShips and Horizon that ship dry goods ? commodities, household items and industrial parts.

Taulli and other market observers say from an investor?s point of view, most of the dry goods carriers offer a way to profit from the growing Chinese economy.

China?s manufacturing output has created high demand for raw materials ranging from coal to steel, and much of the transport depends upon marine shipping. DryShips, Diana Shipping and TBS have cited China specifically as a major factor affecting their freight demand.

The available cargo space to hold these materials is tight, with some firms operating their ships at close to 100 percent capacity.

Most are in the process of ordering new ships or buying used ones, but in the meantime, the low-capacity, high-demand environment means one thing: The ability to charge higher rates to customers.

?There?s only so many ships and so much capacity available,? said Adrian Gonzalez, a logistics expert at ARC Advisory Group Inc. in Dedham, Mass. ?We?ve definitely seen rates increase on the ocean side.?

Those rates have translated into a cyclical high for dry goods shippers. Average rates in some cases have doubled from 2003 to 2004, and the effects can be seen on profits at dry goods shippers.

Athens-based Diana Shipping, which could go public as early as this week, tripled its net income to $28.5 million in the first three quarters of 2004, compared with all four quarters in 2003.

It expects to boost its dividend to shareholders as a result of capital from the IPO and increased revenue brought in from new ships it is adding to its fleet.

TBS International, which is based in Bermuda and specialises in servicing ports that require smaller ships, swung from a loss of $2.8 million in 2003 to a profit of $41.9 million in 2004. It doesn?t plan to pay a dividend.

Horizon Lines, a Charlotte, N.C., shipper which focuses on routes to Alaska, Guam, Hawaii and Puerto Rico, saw its operating income rise 35 percent in 2004, but its net income declined ten percent to $13.6 million as its interest expense tripled.

The rising interest expense is related to the financing of its acquisition last year by private equity investor Castle Harlan Inc., which plans to pay itself and other existing shareholders a special one-time dividend after the IPO, and will pay an ongoing regular dividend to other stockholders.