Re: A man under the water or in the water?
If you're talking about people, then they are "in the water" if their head is still up in the fresh air, breathing, and they're "under the water" if their entire body, including the head, is underwater.
However, if you are specifying a part of the body, you might say something like "his shoulders were under the water". Obviously, it can't be only his shoulders but he is under the water up to and including his shoulders but his head is still above water.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.