The XPRIZE Foundation, once known for competitions for spaceflight innovation, has turned its focus to the seas, launching a series of new prizes for ocean health over the next seven years.

The Ocean Initiative represents the biggest XPRIZE commitment to date, reinforcing earlier competitions for devices to monitor ocean acidification and clean up oil spills.

"The oceans are in trouble. They have been under attack for the last half century, and we do feel we are at a tipping point right now," said Wendy Schmidt, who is sponsoring the prizes, and is president of the Schmidt Family Foundation and co-founder of the Schmidt Ocean Institute.

The prizes mark the first time the XPRIZE has decided to concentrate on a specific research area. "Prizes in the past have been serendipitous – whatever comes along," Schmidt said. "Getting this much focus on the inner space is definitely an important thing, I think, for this generation."

Scientists say oceans remain the last great unknown – and research funding is drying up. Outfitting research vessels or embarking on "grand projects", such as mapping the ocean floor, remain prohibitively expensive, out of reach of government scientific agencies or public research institutions.

Meanwhile, oceans are under threat from climate change, which is changing the chemistry of sea water, overfishing, and plastic pollution.

The competition launched on Tuesday will invite the public to help design the challenges for innovators, with a view to awarding between three and five prizes over the next decade.

Potential competitions include prizes for innovations in dealing with dead zones, such as those in the Gulf of Mexico, overfishing, which is threatening global food supply, or the great Pacific garbage patch, a vast swathe of remote ocean strewn with plastic debris.

The XPRIZE Foundation took a first dive into ocean health in the wake of the BP oil spill, offering $1.4m prize for the creation of a more efficient oil spill clean-up device.

The foundation last month returned with a new $2m prize for devices to monitor ocean acidification.

With the latest prize announcement, Schmidt and Peter Diamandis, the chairman of the XPRIZE foundation, said they would appeal to the public, as well as seek expert advice, to identify the most urgent challenges to ocean health. "There is not very much money being spent on ocean research, and the impact on humanity is so large. This might be a great place for crowd sourcing to have an impact," Diamandis said.

The prize competition last month announced a $2m competition for devices that can monitor the changing chemistry of the oceans due to climate change.

Oceans have absorbed nearly a quarter of the greenhouse gas emissions that are responsible for climate change.

With greenhouse gas emissions, oceans are now about 30% more acidic than during the pre-industrial age, a shift that is devastating coral reefs and fisheries, and threatening food supplies.

The $2m competition announced last month will be split into two prizes – one aimed at research institutions for a highly accurate deep-water acidity monitor, the other for a more affordable monitor for shallow waters. The prizes will be announced in 2015.