Swimmies means: A derogatory term used to describe members of the Socialist Workers party. This Trotskyistfar-left political party is based in Britain and Ireland, which places much emphasis on direct actions. At any protest against Israel or the US, you will find swimmies either giving out copies of the party newspaper, or holding placards with the words “Socialist Worker” printed boldly in italic helvetica. (in Community Dictionary, added by Cándida Ramos)