Some people develop swelling of the hands and feet when they are exposed to heat. It appears that this is what happened to you. The exact cause is not known but it is likely that the swelling is the result of excessive dilatation of the blood vessels and consequent leak of fluid from within the blood vessels. I would suggest that you continue to swim regularly and then shower in luke warm or cold water (depending on the water temperature). Exercise is good for you so I would not advise you to abandon swimming.