As long as you are fine with the arrangement, it should not be a problem. The only other consideration would be the possibility of a predator being able to climb onto the island via the dock. Is this possible? Do you have raccoons, alligators, foxes, coyotes, panthers, domesticated pets such as dogs, cats, etc.? If so, then this may not be the ideal situation.

If predators are not a concern, and you want to entice the swans for nesting, you might want to get some hay (coastal hay) (DO NOT USE PINE STRAW as the resin can mess up their feathers) and place it on the dock. Of course, you may also entice other species such as ducks and geese to also nest and you will need to occassionally clean the fecal matter from the area when not being used for nesting. The Regal Swan