The hooded merganser is a sexually dimorphic species. Along with the smew and hooded merganser, they are therefore often known as "sawbills". The hooded merganser, often termed "Mergus cucullatus", is not of this genus but closely related. The hooded merganser is a diving predator that largely hunts by sight while under water. The hooded merganser has a sawbill but is not classified as a typical merganser.