Electric Eels

Creatures (robots, monsters, aliens) entities
Actually they are 80% air breathing knifefish (not eels) that can generate electric shocks up to 500 volts & 1 amp for self defense or attacking prey.

In reality, electric eels are found in South American waters mostly associated with the Nile. Freshwater rivers, floodplains, swamps, creeks, & muddy water bottoms are favorable. The do mind neither flowing or stagnate waters. However, videogames authors may stretch their range (and abilities) to anywhere in order to provide a deadly obstacle to a protagonist. An underwater cave is an unlikely place to meet a fresh-air-dependent electric eel, unless its within a videogame. In videogames, the power of an electric eel shock is usually not exaggerated and perhaps even down played, A real electric eel is quite capable of killing a healthy adult human with a single shock.