Ah, the seas of the Triassic. There's nothing like them...if this is your time.
Just beneath the surface, various ichthyosaurs swim. They swim in schools, or they swim alone...or in pairs. Like reptilian billfish, they set an epic precedent for fish...if not reptiles.
Among them, the first plesiosaurs swim. Like fin-footed sauropods, they struggle to compete with the ichthyosaurs.
At various depths, placodonts and askeptosaurs swim. They're marine reptiles...like the ichthyosaurs, only...more reptile-looking...
In various depths, the saurichthyids and birgeriids swim. They're ray-finned fish...and among the first.
In deeper depths, chimaeras swim. Their skeletons are made entirely of cartilage. Their descendants will, one day, become the first sharks.
Very deep down, the first tube worms, the serpulids, take root. They're annelids. One day, their descendants will become earthworms and giant tube worms.
In various depths, the first nautiluses, the ammonites, swim around, backwards. Their tentacles are much longer than today's nautiluses...and their shells are broader.
Inshore, there are corals. The reefs are long, and vast.
Above and around the corals, nothosaurs swim. They're ferocious, and relentless.
Farther inshore, phytosaurs either rest on land, or swim around among the coral. When they take naps, they really die. They're the crocodiles of this time period.
Up the shore, there are cynodonts; the mammals' precursors. Some resemble sea lions. Others resemble sea otters. They dive into the sea and swim among the corals, chasing the local saurichthyids and birgeriids. Even here, they have to compete with not just the phytosaurs, but the nothosaurs, the placodonts, and the askeptosaurs...as well as a few of the more aggressive ammonites. These days, not even seal-like cynodonts can compete with the reptiles...
Yes, Triassic sea life is impressive. Alas, there's also freshwater life, farther inland...
Welcome to Lake Tethys. Out here, it's surrounded by mountains and deserts. Some who ever came out here would likely think of Lake Tahoe. A few rare specimens would think of Lake Titicaca. At this point in history, as most of the continents are still merged, they're one in the same lake.
Beneath the surface, and in some cases beneath the bottom, and in caves, the first lungfish slumber. They love to hibernate. Every now and then, they like to breathe air. In this day and age, lungfish are bigger than anacondas. Whether they're just as dangerous has only been learned by a few. Time travelers, to be more specific.
Closer to the surface, the larvae of temnospondyls, the first amphibians, swim around. These days, tadpoles are as big as fish, and waterdogs are more like baby crocodiles.
Ashore, relatively freshwater phytosaurs rest on the bank. Whenever they like their chances, they charge into the water, charge through it, and seize their prey by its weak spots. Mostly, though, there's no show to see. But then, today's crocodiles haven't evolved much from their prehistoric kin.
Ashore, and in the shallows, there are otter-like cynodonts. They take to the waters and play around, like their descendants. On a good day, they playfully harass the phytosaurs. To them, life's a ball.
Alas, the lungfish aren't the only monsters that inhabit the depths of Lake Tethys. Some are far more dangerous.
In the shadows, a few of the first piranhas swim around. In reality, they're more like vultures, in the way they feast. Alas, all they've got to do is sense blood in the water...
In the caves, they swim around. Their stomachs growl. It's been quite a while since the last time they've fed. But then, in the future, vultures will feel the same way.
Playfully, some of them bite at one another. On a good day, they bite back...and the fight is on. Without luck, they eat each other. Without luck, they never eat at all.
Ah, monotonous, yet peaceful, is the life of a Triassic piranha. For these, alas, it's about to get a bit steamier...