[rm_-rf_slash]

What would they record it on? This seems to me the biggest drawbacks of seaborne intelligence: any dolphin could be twice as smart as the smartest human but it's really hard to develop technology when you don't have opposable thumbs and the environment is, almost by definition, more fluid and corrosive than the one we share.

[bostik]

Hah, that sounds almost like something out of a book.

"For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons." - Douglas Adams, H2G2

Although I do think that without a way to store knowledge outside the brain it becomes much harder to form and maintain societies. Ian Stewart uses a wonderful term for that part of intelligence which we cannot hold inside our heads: extelligence. An external store of knowledge and (mis)information allows for sources of reference even when no other people with the knowledge happen to be available.

[Asbostos]

It's not that bad. The undersea environment doesn't suffer from erosion and weathering which basically prevents any long term construction from surviving very long on in the air. If dolphins carved words into the sea floor using a tool, they could easily be very long lived.

[rm_-rf_slash]

What would the tool be made out of? Would any rock do or would it have to be a specific type that requires modification? What would they hold it with?

[eru]

Why no erosion? There are still currents.