The Scottish Seabird Centre wants to expand its education and conservation programmes to include all marine life in a bid to remain viable.
A National Marine Centre for Scotland is designed to be built at the existing Seabird centre in North Berwick.
An interactive experience is planned to inspire people to care for the natural environment above and below the waves.
The Scottish Seabird Centre said it needs to evolve to remain viable, it has more education requests than it can cope with and visitor expectations are at an all-time high.
It has secured £3.3m Heritage Lottery funding but needs another £2m if its vision is to become a reality with the centre planned to open in 2020 for Visit Scotland's year of coasts and waters.
Grace Martin, project director for the National Marine Centre, said: "The Scottish Seabird Centre currently offers visitors an opportunity to engage with nature in a sustainable way.
"As a conservation and education charity, we welcome 4,000 schoolchildren a year and lead projects such as SOS Puffin.
"But, as with all charities, we must move with the times to remain viable and to achieve our objectives of inspiring people to care for wildlife and the natural environment.
"We have more education requests that we can accommodate and visitor expectations are at an all-time-high.
"Our vision is to create a centre that is of national significance and one that the local community is proud of."
Professor John Baxter, principal advisor at Scottish Natural Heritage and a trustee of the Seabird Centre, said: "The marine environment of Scotland supports a fantastic array of habitats and wildlife.
"Under the surface of the seas is a hidden and very special world that we want to reveal and bring to life, for people of all ages, in exciting and engaging ways.
"Scottish universities are at the cutting-edge of marine environment research but there are at present limited opportunities for the public to share in this work.
"Through public engagement we know there is a high level of interest in our seas, coasts and wildlife.
"This new attraction will provide an immersive and interactive experience, communicating the latest research and inspiring people to look after our natural world. It is vital that we protect and conserve our seas and their wildlife for future generations."
Plans for a £5.5m National Marine Centre for Scotland have been unveiled in East Lothian.