Redtailfool got there first,
Ogilbia pearsei and Dama ciega blanca are both correct! This is one of the very few fresh water cusk eels, most are abyssal fish and the the few fresh water members of the order are cave dwellers. This one is actually fairly comman over much of the Yucatan penninsula and even show up in wells.
ugly little s---s! Good job guys!