Congo eel and Conger eel

Congo eel noun - Aquatic eel-shaped salamander having two pairs of very small feet; of still muddy waters in the southern United States.

Conger eel and congo eel are semantically related. In some cases you can use "Conger eel" instead a noun phrase "Congo eel".

Conger eel noun - Large dark-colored scaleless marine eel found in temperate and tropical coastal waters; some used for food.

Congo eel and conger eel are semantically related. Sometimes you can replace phrase "Congo eel" with "Conger eel", this phrases are similar.