for dear life

少年向けの小説 "Mad Scientists' Club"も終わりに近づきましたが、作者の子供がインターネット上に "Mad Scientists' Club" - Official Mad Scientists' Club Web Siteを下記アドレスに作っている事を見つけました。
http://www.madscientistsclub.com/books.html
興味のある方は見てください。
さて今日とりあげる表現を含む文です。
He just dove over the stern of the boat and swam for dear life.
"for dear life" は慣用句のようなので辞書で確認します。
・OneLook Quick Definitions: as though your life was at stake ("He was running for dear life")
・Cambridge Advanced Learner's English Dictionary: If you do something for dear life, you do it with as much effort as possible, usually to avoid danger; As the ship began to tilt, we clung on for dear life.
・Dictionary.com: with desperate effort, energy, or speed: We ran for dear life, with the dogs at our heels. Also, for one's life.
"for dear life" は必死にならずとも憶えられそうなフレーズですね。