aqualung
From Longman Dictionary of Contemporary Englishaqualungaq‧ua‧lung /ˈækwəlʌŋ/ noun [countable] trademark British English DSSa piece of equipment that provides a diver (=someone who swims underwater) with air, and which they wear on their backsExamples from the Corpusaqualung• So Thomas played bridge with them, and swam, and learned to use an aqualung.• This was brought home to me many years ago when I dived into the River Kennet with an aqualung.• This was all happening half a century ago, before the invention of the aqualung.