In this case report we describe the clinical and laboratory findings of a man who nearly drowned after aspirating a large quantity of seawater. The aspiration of salt water, which is strongly hypertonic with respect to plasma, resulted in severe pulmonary edema, both from the quantity of aspirated seawater and the osmotically driven ultrafiltrate of plasma that accumulated in the air spaces. The initial concentration of protein in the edema fluid sample was very low, 0.7 g/dl, consistent with only a minimal increase in epithelial permeability. Approximately 4 h later, there was a marked increase in the concentration of protein in the residual alveolar fluid associated with improvement in several clinical indices, indicating that the excess alveolar fluid was reabsorbed very rapidly. In addition, the magnesium concentration was markedly elevated because of the aspiration of magnesium-containing seawater, which may have diagnostic importance for near-drowning in salt water. The data from this case provide evidence for well-preserved alveolar epithelial barrier function after aspiration of large quantities of hypertonic salt water.