Drowning Is Often the Introduction of Outside Water into the Alveoli

Drowning is often the introduction of outside water into the alveoli, yet some water is normally present in alveoli.Why is water normally present in the alveoli? What is present in alveolar fluid, besides water, that aids in respiration? What properties of water are detrimental to respiration? What causes drowning? While extremely rare, there have even been documented cases of people walking away from recreational swimming only to die later, on dry land, as a result of drowning (termed "delayed" or "secondary" drowning).Propose an explanation for delayed drowning.