There's big doings on the oceans these days, and big business is wondering about the ripple effects.

The world's three largest ocean carriers—Maersk Line, CMA CGM Group and Mediterranean Shipping—are forming an "alliance" on the trade routes connecting the world's three biggest economic centers: North America, Europe and Asia.

That means the carriers will share ships traveling on the Atlantic through the Suez and Panama canals into the Pacific. They will also share port facilities in transportation hubs from Shanghai to Los Angeles and New York, and on into Rotterdam, the Netherlands.

That worries the manufacturers and retailers that use shipping lines to send their products and supplies globally.

"It's enormous," said Bruce Carlton, president of the National Industrial Transportation League, a group that lobbies on transportation issues for U.S. businesses. "It's so big it raises immediate, obvious questions about the market implications, of pricing and competition among the carriers."

The so-called P3 alliance will give the three carriers control of about 43 percent of the Europe-Asia shipping market, 24 percent of the trans-Pacific, and 40 percent to 43 percent of the trans-Atlantic, according to figures cited by the Federal Maritime Commission, the U.S. agency that regulates ocean-shipping services.

"The fear most shippers are probably going to have is the sheer size of the thing," Simon Heaney of Drewry Shipping Consultants, said in an interview. "Alliances are nothing new, but this is taking it to another tier."

Maersk, based in Denmark; CMA CGA, based in France; and privately owned Mediterranean Shipping, based in Geneva, control about one-third of the world's shipping fleet, according to Drewry. The fourth largest is Taiwanese carrier Evergreen.

Past shipping alliances have been restricted to particular trade routes and economic theaters. The carriers have used such alliances as a selling point with their shipper customers, since the alliance, by pooling equipment, typically allows them to offer more frequent service to more ports.

Say you're a widgetmaker and you regularly ship your product to a retailer in Germany. You typically use X Ship Lines. But if X Ship Lines forms an alliance with Y Ship Lines, your widgets could now get to Germany on a Y Ship Lines vessel. Instead of waiting every two weeks to send your widgets to your retailer, you can now do it weekly. While the widgets may have traditionally been routed via Bremerhaven (because that's where X Ship Lines has a terminal), they can now go via Hamburg (closer to your retailer) because Y Ship Lines has a terminal there.

"Over the years, shippers have certainly benefited from these alliances," conceded Carlton of the NITL, which has 400 members. But in the case of this P3, "we really don't know anything about the economic impact or market impact."

It's transport pricing, one of the basic inputs of production, that's at the heart of business concerns.

"What the customer wants to hear is the impact on the bottom line," said Carlton in an interview. "Are prices going to go up or are prices going to go down?"

Shipping lines have historically been allowed to collude, but changes to regulatory regimes around the world and basic economic competition has eroded that pricing power.

In the meantime, various lines have been buying fuel-efficient and larger ships, adding to the general supply of capacity when demand—because of the flagging world economy—is down. That has depressed shipping prices and kept them volatile over the past few years.

"They simply can't control revenue at this time," said Drewry's Heaney. "It's all about being cost competitive now."

By sharing equipment but expanding service offerings, the P3 alliance is aimed right at containing costs, proponents argue.

"The three things the P3 gives us are coverage, frequency and stability," said a Maersk spokesman. "That's the value it provides not just us, but our customers as well."

Still, there are worries that the alliance could serve as a way for the three carriers to restrict supply, thereby driving up freight rates.

"One of my concerns relates to media reports that a combined east-west fleet of 346 vessels will be reduced to 255 vessels once the proposed Alliance is consummated," said Federal Maritime Commissioner William Doyle in a statement issued by the agency.

The commission is reviewing the P3 alliance proposal, as are regulatory authorities in Europe and Asia. Unless they move to block or hold up the alliance, the alliance will go into effect in the second quarter of 2014.

—Allen Wastler is managing editor of CNBC Digital. Follow him on Twitter @AWastler. You can catch his commentary here and on CNBC Radio. And check out his fiction.