If you say that a place is not sanitary, you mean that it is not very clean. It's not the most sanitary place one could swim. = hygienic
Of or pertaining to health; designed to secure or preserve health; relating to the preservation or restoration of health; hygienic; as, sanitary regulations
free from filth and pathogens; "sanitary conditions for preparing food"; "a sanitary washroom"
Sanitary means concerned with keeping things clean and healthy, especially by providing a sewage system and a clean water supply. Sanitary conditions are appalling