Stop messing about! You'll get water in your ears!
You don't want water to get in your ears, do you? Keep still and stop moving around.
You don't like it when water gets in your ears, do you? Keep still while I wash your hair.
これは世界中のお母さんがよく言う台詞ですね＾＾
Stop messing about! You'll get water in your ears!
（遊ぶのを辞めて！お耳に水が入っちゃうから！）
※messing about ＝ 遊ぶ・ふざける
You don't want water to get in your ears, do you? Keep still and stop moving around.
（水が耳に入るといやでしょう？じゃあ、動かないで。）
※keep still ＝ 動かないで
You don't like it when water gets in your ears, do you? Keep still while I wash your hair.
（水が耳に入るといやでしょう？じゃあ、ママがあなたの髪の毛を洗う時に動かないで。）
こちらのフレーズ（命令！）も役に立ちます：
Stop splashing!
※ splash＝水をはねかける
Stop wriggling!
※ wriggle＝くねくねする
Don't move!
Close your eyes!
Keep still!
Keep your head still!
イギリス 
