Black-winged hatchetfish (Carnegiella marthae)
The most obvious trait of the freshwater hatchetfish is their enormously enlarged sternal region. This is accompanied by large pectoral fins and extraordinarily powerful associated muscles which account for up to 1/4 the total body weight. Quick beats of the pectoral fins allow hatchetfish to lift themselves half out of the water and glide along the surface … Some species can even leave the water for short stretches of up to 2m. This allows them to quickly escape predators.