SOLVED. Fantasy/Science fiction with ultra intelligent dolphins? [s]

[Kim]

I read this book maybe 8 or 9 years ago, but i think it was published in the 80s or 90s. Its a book for ages 11-14. It's filled with a lot of pictures, and the story is a bit odd...in it a group of people travel around in a submarine and find like a hidden utopia where there's an advanced society of dolphins. They have hand like flippers and I remember that in one part there was a dolphin who was a doctor. It's titled something like "the hidden/secret/lost world/utopia". The edition I had like a large picture book with text within the pictures. the cover was a person in a lagoon in front of a waterfall.

[Leonie]

My first thought was Startide Rising by David Brin, but I don't think all the details match.

[Kim]

Leonie wrote: "My first thought was Startide Rising by David Brin, but I don't think all the details match."

nope not that one, thanks though!

[Adele]

It sounds like The Secret Oceans except the cover doesn't match.

Actually, the cover does match - I didn't see the waterfall way in the background. I think this might be your book!

[Ayshe]

The Secret Oceans maybe?

[Kim]

THAT'S IT! You guys are amazing! I didn't think anyone would able to find it! Thanks so much!