We report an unusual case of post-mortem redistribution of ethanol in a woman diver who died by drowning in seawater. The ethanol concentrations were right heart blood 0.60 g/l, left heart blood 2.08 g/l, femoral venous blood 0.63 g/l, gastric contents 5.87 g/l, bile 0.83 g/l. The mechanisms of post-mortem redistribution of ethanol described in the literature, that is, early redistribution from the stomach or the lung parenchyma in the case of inhalation of gastric contents, are inadequate to account for the degree of variation observed between the measurements. We believe that this difference in concentration is explained by the presence of seawater in the pulmonary alveoli at the time of death.