What is Omega 3 Fish Oil? Fish oil is oil obtained from the body of the fish, rather than the liver. It is a natural source of Omega 3 essential fatty acids (EPA & DHA) & Vitamins A & D. What Does Omega 3 Fish Oil Do? DHA contributes to the maintenance of normal vision & normal brain function. EPA & DHA contribute to the normal function of the heart & to the maintenance of normal blood pressure & triglyceride concentrations.