A seahawk is a real bird; it is a colloquial name for an osprey. The osprey also goes by other names, such as fish eagle and river hawk.
The osprey is a predatory bird adapted for hunting and catching fish. An osprey preys on fish almost exclusively and is the only raptor with backward-facing claws. These claws help an osprey hold onto prey. The bird also has tiny spines on the soles of its feet to help it clutch onto prey. Osprey wings have an "M" shape and span up to about 71 inches. The birds grow up to about 23 inches long.