A disoriented whale that turned up at a bustling Buenos Aires marina has nearly found its way back to the sea but is still stuck in fresh water, an official said Wednesday.

"It's at the mouth of the River Plate, in the area we call the ante-port. It's almost on its way. It's just one small step from swimming out to sea," a city hall spokesman told AFP.

The small humpback whale surprised passersby by surfacing Monday amid the yachts docked in Puerto Madero, the Argentine capital's upscale waterfront neighborhood.

It had apparently strayed off course, leaving the Atlantic Ocean and swimming up the River Plate estuary into a canal that serves the marina.

The coast guard, environmental officials and marine biologists have been working to lead the whale back to sea, in an operation using seven rescue boats.

But experts warn the whale may struggle to survive after spending more than 48 hours in fresh water.

"It's supposed to be in seawater, which is its habitat. As long as it's in the river water, it's at risk and there's no way to save it except to accompany and guide it," said Miguel Iniguez, head of the Cethus Foundation, a conservation group devoted to protecting whales.

Photos of the whale show it has injuries on its skin.

Iniguez said the whale's wanderings may be a sign of illness, "but it's hard to know what health problems it has."