What invertebrates can be found in freshwater?

Crustaceans include crabs, crayfish, shrimp, and barnacles. Insects include mayflies, dragonflies, and walking sticks. Mollusks include clams, mussels, and snails. Worms include earthworms and leeches. Echinoderms include starfish and sea cucumbers.

Most of those are freshwater but some are saltwater like starfish right?

There are a bunch, some include snails, shrimp, freshwater crabs, eels, and more.

Yeah, there are loads, too many to name in fact. It seems like a lot of people are surprised by the fact that there is more life in the water happening than in most areas on the planet.