A unique community of hundreds of eels has been discovered at the site of an active, underwater volcano near Samoa.

Researchers from the University of Sydney made the discovery as they explored the Vailulu'u volcano using a manned Pisces V submarine after a new volcanic cone was found.

"They discovered a number of large communities of eels inhabiting the fragile cavernous rock pillars surrounding the hydrothermal vent area," senior lecturer in marine science, Dr Adele Pile said.

Scientists had dubbed the marine hydrothermal community "Eel City", she said, adding the team did not know why such an extensive eel community surrounded the volcano.