The term 'slender fish' can refer to four different species of fish: eels (4 letters), EEL (3 letters), GAR (3 letters), and saury (5 letters). Eels are elongated, snake-like fish found in both fresh and salt water. The EEL is a type of EEL found in the Atlantic Ocean and Mediterranean Sea. GAR are long, slender fish found in North American freshwaters. Lastly, saury are slender, silvery fish found in the Pacific Ocean.