I have been looking for a children’s science fiction book I read in elementary school in the 1960’s. All I can remember is that there was a planet (might have been earth) covered in water and dolphins who helped or played a role in the story. There might have been more than one book that were related.
Stump the Bookseller
New format, same book stumper solving.
You might look into some of Andre Norton’s books. There was one from a series set in a water world. Also, could be the Dolphins of Pern by Anne McCaffrey.
OK, this is not too like your book, but children’s SF, published in the 60’s involving dolphins: Dolphin Island, Arthur C. Clarke. Boy runs away from home on hovercraft; hovercraft crashes into ocean; boy rescued by dolphins and ends up on Dolphin Island, where they are doing research on how to talk to Dolphins. Adventures ensue.