The centre aims to be a world leader in aquatic research
A proposal to loan an extra £400,000 to the firm behind plans for an aquarium complex in Bedfordshire has been agreed by councillors.
The National Institute for Research into Aquatic Habitats (Nirah) plans to build the £375m aquarium in Stewartby.
The latest loan agreed by the county council comes on top of other loans amounting to more than £3m.
Richard Stay, deputy council leader and on the board of Nirah, said the council would get its money back.
The aquarium would also be a scientific research centre and a visitor attraction, four times larger than the Eden Project, in Cornwall.
Mr Stay said: "There is value in the intellectual property rights, the planning permission and the actual land value which more than adequately covers the value of the loans made to Nirah.
"So if Nirah doesn't happen, we stand a pretty certain chance of getting this money back."
Liberal Democrat county councillor Susan Gaszczak said: "Although it is an amazing concept... it is a time of a global credit crunch.
"It is a very difficult time to start raising that kind of money, and especially when you see the taxpayer suffering on a day to day basis."