What is the name of a primitive freshwater animal which looks like eel?

There are several freshwater animals that look like eels, but the most likely one you're thinking of is a lamprey.

Here's why:

* Appearance: Lampreys have a long, slender, eel-like body with a sucker-like mouth.

* Freshwater habitat: They are found in freshwater streams, rivers, and lakes.

* Primitive: Lampreys are considered a primitive fish group, having existed for millions of years.

However, there are other possibilities, such as:

* Caecilians: These are limbless amphibians that can resemble eels. They are primarily found in tropical regions.

* Freshwater eels: Some species of eels, like the American eel, are found in freshwater environments.

To be more specific, please provide any additional details you remember about the animal, such as its size, color, or behavior. This will help me narrow down the possibilities.