I often think that a big reason we developed as much as we have is due
to strife from our environment. The Ice Age, for example, forced early
humans to make and build things to survive the cold and when the world
did get warmer again, they had all these neat tools, ideas, and experiences
to expand upon.

I could be wrong here, not being an oceanographer and all, but maybe
the oceans even with their own adversities also provide enough resources
to keep its residents happy with no need to expand upon things.

Or maybe, while cetaceans and such are relatively smart, they just
aren't smart enough to build underwater cities and star cruisers. Maybe
only land creatures have the correct environment for serious development.

I know I am biased being a land-based creature and all, but either the
whales and dolphins and octopii are really taking their time getting
around to tool use and engineering, or they are never going to do it.

Or maybe in another 10 million years they will surprise me, just as an
ETI coming to Africa 5 million years ago might not have thought much
of the primates hanging out in the trees there.

Waiting for Phil to say, it's always in another 10 million years. :^)