 Immersion pulmonary edema IPE is a condition in which fluid fills the lungs during diving or swimming, particularly in cold water. Some individuals appear to be predisposed to developing IPE. DNA samples will be collected and stored, in order to compare the genetic profiles of individuals who have experienced IPE with those who have not. In a few individuals who have experienced IPE, we plan to measure the effects of cold water immersion on the blood pressure, cardiac output and the pressures in the pulmonary artery. These will be compared with similar measurements already obtained from normal individuals. 