60 meters

Encyclopedia Britannica

loon (bird) -- Britannica Online Encyclopedia

Almost wholly aquatic, loons can swim long distances underwater and can dive from the surface to a depth of 60 metres (200 feet).

avianweb.com

Great Northern Divers, known in North America as Common Loons

This species, like all divers, is a specialist fish-eater, catching its prey underwater, diving as deep as 200 feet (60 m).

a-z-animals.com

Common Loon (Gavia Immer) - Animals - A-Z Animals - Animal Facts, Information, Pictures, Videos, Resources and Links

The common loon has been seen diving as deep as 200 feet (60 m) to get its lunch.

thecursedcow.blogspot.com

October 2010

The common loon has been seen diving as deep as 200 feet (60 m) to get its lunch.

boating.ncf.ca

Pat's Boating in Canada: Loons

They are able to concentrate oxygen in their leg muscles to sustain them during dives as far as 60 meters (200') below the surface.

80 meters

eHow

What Birds Are Penguins Most Related To? | eHow.com

This helps the loon dive up to 80 meters, but requires the birds to run on the surface of the water for up to several hundred meters before they can take flight.

75 meters

goddidcreations.com

Bird Facts - fun facts about our feathered friends

The common loon can dive more than 76 metres below the water's surface.

thewonderofbirds.com

The Loon or Diver in Flight and Diving on the Water

Loons are are superb divers (hence their alternative name), who can go to depths of up to 75 meters below the surface and can remain under water for up to eight minutes.