Spiny eels are elongated, freshwater fish, known for their unique eel-like shape and the rows of spines along their backs. They are not true eels, but rather belong to the family Mastacembelidae and are found in tropical regions across Africa, Asia, and parts of Australia. Spiny eels are typically nocturnal, bottom-dwelling fish, preferring sandy or muddy substrates where they can burrow and hide.