Logic Riddles

Question: If there were ten fish in an enclosed tank, and four swam away, three died, and three drowned, how many fish would be left?

Question: A girl dived in the sea.. some say there are two humans under the sea. Why is that?

Question: I'm priceless, and cannot be bought, Some seek my purpose, Others destroy me, Those who steal me gain no more, I never last forever, but can a life-time. What am I?

Question: Why do cows wear bells?

Question: A cowboy rode to an inn on Friday. He stayed two nights and left on Friday. How could that be?