There were three men on an airplane somewhere above the atlantic ocean. Suddenly Death apears on the plane. He says"Before I take you all with me 'll give you a chance to survive. Each one of you will throw something to the ocean and if I find it you will die".

The first one throws a needle. Death goes down to the ocean searching for it. After a couple of minutes he comes back with the needle

The second one throws a hair. Death goes down and after ten minutes he comes back with the hair

The third one throws quickly something and Death goes down again. About an hour later he comes back and says to the guy "Ok you win, I'll let you live.But tell me what did you throw?

The guy says "An effervescent tablet"