Is it permissible to expose one's 'awrah while swimming?

It is not permissible to expose one's awrah to anyone, whether while swimming or otherwise, except between spouses or for the necessity of medical treatment with a doctor. This is based on the words of the Messenger of Allah, peace and blessings be upon him: "Guard your awrah except from your wife or what your right hand possesses... If you can ensure that no one sees it, then do so... For Allah, the Blessed and Most High, is more deserving that one should feel shy before Him."