Two men on a ship

Question: Two men were on a ship. They were both facing opposite directions, one facing east and the other facing west. But, they were both seeing each other. *WITHOUT MIRRORS* How is this possible?

Question: Surrounded by life , yet life is its biggest enemy. But without life there is no need for it to exist. What is it?

Question: During what month do people sleep the least?

Question: When is 99 more than 100?

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?

Question: The more you add, the less it weighs.