Question 6: On the ninth and tenth of Muharram, Muslims wake up early, go to rivers and swim there. They claim that Allaah (Exalted be He) replaces the water on this day with fresh water. After sunrise, men and women shake hands. What is the ruling on this in Islaam?
Answer: Men swimming with women and then shaking hands on the ninth and tenth of Muharram is a great Munkar (that which is unacceptable or disapproved of by Islaamic law and Muslims of sound intellect) and impermissible. Those who do so must be reproved, and the governor should stop them from doing so... read more here.