screen door on a submarine

English

Etymology

The idea of a screen door (mesh door to keep insects out) on a submarine is considered to be highly impractical. There are no insects underwater for a screen door to keep out. A screen door also allows water to pass, so it would cause the submarine to sink if it's the only door between the interior and the outside world.

Noun

screen door on a submarine (plural screen doors on a submarine)

1. (idiomatic) something that is useless or absurd
   • 1995, The Economist‎^[1], volume 336, numbers 7921-7925, Economist Newspaper Limited:

     But realists put the final number of jobs saved through privatisation at no more than 800. "It's about as useful to us as a screen door on a submarine," says an angry mayor's office in Sacramento .

   • 2005 July, Rich Beattie, “Trigger Happy”, in Boating‎^[2], volume 78, number 7, →ISSN, page 123:

     I doubt anybody would give you static about unloaded and stored long guns anywhere in U.S. waters, and few places would about handguns (although unloaded guns are as useful as a screen door on a submarine).”

   • 2016, Rocky Heckman, Designing Platform Independent Mobile Apps and Services‎^[3], John Wiley & Sons, →ISBN:

     If you don't know what security vulnerabilities look like at the code level, then having the source code is just as useful as a screen door on a submarine from a security perspective.