English Gone Wong!

It would be very clear to native English speakers that this sign is instructing the viewer that there is a danger that you may drown if you are not careful. I think they must have tried to say "Be careful or you may drown". Now however, it sounds as if they have tried to put that sign for those who come to that river (or whatever) to kill themselves or try to drown their companions. Indeed, if you try to drown yourself and others by making too much fuss, you may mess up your killing attempt as it would unnecessary draw public attention. Hence, they tell you to do it carefully, i.e. doing it quietly when no one is looking.

 

 One shouldnt use the lift if it catches fire. Although if you're in the lift when it catches fire, you'd be dead in no time. If you are not in the lift when it catches fire, I dont think you would be able to use it anymore. It is kind of obvious. But after all, many people lack common sense (especially the Chinese) and it'd helpful if they have given you basic instructions to save your ass.

Thanks to 'Gaurav' for these examples of Chinese translation.