Just thought to expand the topic a little more.
What is pictured in Sue's question is floating nest for birds. There are a number of birds that prefer the safety of raising their young away from the shore because of predators. Ideally they are not attached to land and are anchored in order to keep it that way. Although floating nest platforms are accessible to predators, a determined pair may successfully defend their young from being attacked.
While some find geese to be a nuisance, others enjoy watching and feeding the birds or hunting them for sport. Since the large birds breed and raise their young near natural fresh water sources, a floating nest platform will attract more geese to your lake or pond. You can make a floating nest for geese using some common hardware items and cedar wood poles and planks. Cedar wood is preferred over other types of wood because it is naturally water resistant and doesn't contain treatment paints or chemicals that could contaminate fresh water. - How to Build a Goose Nesting Box
If one desires to get fancy, here are a few examples of the luxurious models as I call them: Duck & Goose Nesting Boxes and Floating Nesting Platforms
Aged Copper Roof 5' diagonal Gazebo with mother goose sitting on the nest.
Wild Canadian Goose with goslings just hatched! Photo from client in Sacramento, CA
Loons also use these floating nests as seen below:
Loon Nesting Raft Being put out to water.
Loon Nesting Raft with a loon in it.
Guidelines for Constructing and Deploying a Loon Nesting Raft, with illustrations and a materials list, from the Maine Audubon Society.
Many books have this now famous way of constructing a Canada Goose Nest Platform with an anchor. I learned this one some 15 years back or so.
There are various types of nesting structures that will attract
Canada geese including a floating structure as described below. Cut
the material as shown and nail boards onto pole sections. Attach a
washtub or 10" high section of 55 gallon drum to the platform. Drill
drain holes through bottom of tub and cut an escape hatch 6" wide
and 4" high just under the top of the tub. This is for young geese to
exit the tub. Paint the tub an earth tone color and fill 1/3 full with
nesting materials such as grass or hay. Anchor the platform in 2-4 ft.
of water. Nesting structures should be at least 200 yards apart if
they are in view of one another. This will prevent territorial conflicts. - Canada Goose Nest Platform
And what about predators?
Canada geese are highly adaptable and will nest in
a variety of locations. In many areas, islands,
muskrat houses and homemade nesting structures
provide safe nest sites. Where these are not
available, they will often nest in marsh vegetation,
shoreline points or on upland sites where predators
may find and destroy the eggs.
Canada geese usually lay five or six eggs (occasionally
seven). The gander does not incubate the
eggs but remains close at hand guarding the female.
Incubation period is 28 days, and after the young are
hatched both the gander and the goose take care of
them. Canada geese will aggressively defend their
nest and young, often attacking intruders by striking
hard blows with their wings. - Homemade Nest Sites for Giant Canada Geese