The common loon is one of the most familiar and recognizable birds found across Canada, building its nests on the still, secluded lakes that stretch from one coast to the other. Its haunting, drawn-out cry is, for many people, the very sound of the northern wilderness. The bird is so closely tied to the nation that its likeness was engraved on the one-dollar coin in 1987, and this is why Canadians have ever since called that coin the "loonie." The province of Ontario has named the common loon its official provincial bird. Yet despite all its fame, the loon spends the great majority of its life on the water, and it is only rarely seen at any real distance from a lake.

Beneath the surface the loon proves to be an exceptionally accomplished hunter, with a body that seems purposefully built for the pursuit of its prey. Nearly every other species of bird has a skeleton that is hollow and filled with air. The loon, by contrast, is equipped with bones that are very nearly solid, and this added weight allows the creature to submerge and descend through the water with remarkable ease. A single hunting loon can plunge to depths approaching sixty metres and remain beneath the surface for a minute or considerably longer, pursuing fish through the frigid, shadowy water. Its distinctive red eyes are widely believed to help the bird distinguish its prey in the murky gloom below.