The last underwater research lab in the world, an 81-ton yellow pressurized steel tube anchored 60 feet down next to a Key Largo reef, won’t be scuttled after all.

Florida International University announced Tuesday that it will take over operation of Aquarius, an aging but unique underwater facility the federal government had considered putting on the chopping block because of budget cuts.

“For our students and our marine sciences program, Aquarius offers fantastic new possibilities and is a natural fit for the work we are doing in the Florida Keys and throughout the world,’’ said Mike Heithaus, executive director of FIU’s school of environment, arts and society.

Last year, the National Oceanic and Atmospheric Administration, which owns the lab, had called for ending Aquarius’ operation, even though it cost a relatively paltry $1.2 million to $3 million a year to run.

But after backlash from scientists and a campaign led by South Florida political leaders — including Republican Reps. Ileana Ros-Lehtinen and Mario Diaz-Balart — NOAA awarded FIU a $600,000 six-month grant to cover basic maintenance of the facility, which boasts six bunks, a bathroom, galley, science lab and “wet porch” allowing divers easy entry and exit.

Ultimately, the Obama administration agreed the lab was a valuable asset that couldn’t simply be left to rust. Removing it could run up to an estimated $5 million, said FIU biology professor Jim Fourqurean, who will take over direction of Aquarius.

“This is a big, expensive piece of hardware on the bottom of the ocean,’’ he said. “You just can’t leave it there.’’

To continue its operation, however, FIU plans to develop a new business plan for the lab that will rely on financial support from other government agencies, private industry and groups and other universities, Fourqurean said.

Aquarius, the last of more than 60 underwater habitats once in operation around the world, allows scientists to literally immerse themselves for hours, days or weeks in a coral reef community without having to worry about repeatedly surfacing for air or decompressing from long dives. The facility, previously managed by the University of North Carolina-Wilmington, has hosted 117 research missions and also served filmmakers, Navy divers and 40 NASA astronauts who trained for the working conditions of space stations and zero gravity.

Fourqurean said the lab offers a perfect platform for students, faculty and outside researchers to study many of the problems plaguing South Florida’s water, from climate change to pollution and over-fishing.

It also will raise FIU’s profile in the Florida Keys, said Fourqurean, who is director of FIU’s new marine education and research initiative for the Keys. The school will close Aquarius’ current land base, hidden in a neighborhood, and intends to open a new more visible office along the main highway, he said.

“This fits the strategic vision of FIU growing into the Florida Keys,’’ Fourqurean said.