I once speculated on this forum (I can't locate the post now)on a hypothetical civilization that looked to our eyes like a coral reef. Animals and plants living together in a complex, interrelated community. I called it (them) The Coela. They were sessile life forms that resembled our coral animals, sponges, or stromatolites. Each individual polyp would have no intelligence, but collectively they would be a powerful mind. Sort of how neurons working together make up a human brain.

But the civilization was highly advanced technologically. Instead of machines, they bred specialized life forms to do the mechanical tasks they required. They also interfered with genetics and evolution to produce organisms (or alter themselves) to manufacture the exotic chemistries they used, they built enormous structures (like the Great Barrier Reef) that were actually planetary engineering works with specific purposes. They were capable of modifying evolution and climate on their world to suit their needs. They communicated by the release of chemical substances directly into ocean water, or generating and releasing plankton coded with modulated DNA carrying complex messages.

These creatures would live in a totally different time scale, it would take them centuries or millenia to carry out their plans and projects. Human activities to them would be like microsecond events, essentially undetectable, and we would be unrecognizable to them.. The Coela might have analogues of not only our science and engineering, but of our arts, languages, philosophy, mathematics, politics, even war. And we wouldn't even recognize them as being sentient, much less a civilization. The Coela would live in perfect harmony with their environment because they would not see themselves as being separate from the environment. They would see themselves as being the sentient part of the planet, just as we see ourselves as being the sentient part of the biosphere.

Their physics would probably never develop magnets or Leyden jars, or telescopes or nuclear reactors. But they could easily modify their planet's climate by altering ocean currents and atmospheric composition. It just might take them millions of years....

I wish I could find that post. Keyword: "Coela".