Eels were to be a species of fish catchable in the AquariCraft mod. They would have been Second Tier fish and could have been caught utilizing any of the available Fishing Rods with the exception of the Wooden Rod. The eel was planned for use in Aquaricraft, however due to complications it was removed from the project.
All that's known about the eel is that it would have had a segmented body in which the parts would have moved in conjunction. It's currently unknown what species of eel would have been utilized
It's possible and probable that the Eel was to drop Raw Eel, much like how all of the other fish provide raw meat when captured. This meat was more than likely also cookable to create Cooked Eel, which would have probably restored 1.5 Hunger units like the prepared meats of the Tuna and Salmon.
Could have counted towards the achievement "Tier Crossing", and would have been involved in the achievements "The King of Tilapia" and "The Emperor of Tilapia". Also could have counted towards the "Achieving Achievement" achievement.