Does one have to say a Bracha on water? If so, what is it? What if one drinks water very often (a sip every few seconds)? Please explain how this works.

A Bracha should be recited for every meal or "eating session"; drinking water is no different. The Bracha for water is "Baruch Ata Adonai Eloheinu Melech Haolam Shehakol Nihiya Bidvaro" The Bracha should be recited before you start drinking and takes effect until you finish your "drinking session". There are many details related to the laws of Brachot and since they are a daily practice it is worthwhile studying them in depth.