Anytime I see an article that begins with: "The Secrets of...", I grab on to my wallet and my common sense for dear life. Though it has a lousy title most of the information is very good. I do disagree with the "draft off another swimmer" concept. Having placed very well at the Alcatraz Sharkfest swims I can tell you that drafting is dangerous.
Ocean water, albeit a lake or a sea, is usually murky. By drafting you have the potential to swim your nose or throat into a vicious kick if the swimmer in front of you stops to spot and then kicks to regain momentum. Also, does the swimmer in front know where he/she is going? Drafting works well in a pool but not a ocean race.
Secrets of Open Water Swimming by Coach Jared Burg [Link]
My swim club has Open Water Clinics coming up. Check this page often for either free clinics, open water, or otherwise [Link]