How do aquatic birds such as the wandering albatross avoid becoming dehydrated even though they live in an environment that is almost entirely salt water?
They don't actually swallow the salt water.
They excrete excess salt in their urine.
Like animals that live in extremely arid conditions, they are able to survive for long periods of time without fresh water, only drinking when they have access to fresh water on land or from rainwater.
They are able to maintain their osmolarity close to that of seawater by maintaining salt, urea, and trimethylamine oxide levels in their body fluids, thus preventing the salt water from diffusing into their cells.
They actively transport excess salt from the blood into secretory tubules found in special excretory glands.