A 52-year-old Japanese tourist wasfound dead yesterday in shallow waters off Kahala Beach. The woman was found about 150 to 200 yards offshore.  She appeared to have drowned, but investigators are still trying to determine exactly what happened.  A friend of the woman called 911 about 4:30 a.m. yesterday, saying the woman had gone for a swim overnight, but did not return.  A rescue swimmer recovered the woman about two hours later.  She showed no signs of life.