How do hatchet fish blend into their environment when viewed from below?

Hatchet fish blend into their environment when viewed from below by utilizing their unique body shape and coloration. Their flat, silvery bodies reflect the light from the surface of the water, mimicking the play of light on the water's surface. This counter-illumination helps them become nearly invisible to predators lurking below, as they match the brightness of the light above. Additionally, their small size and positioning in the water column further enhance their camouflage against the backdrop of sunlight filtering down through the water.