How to tread water longer?
In order for you to tread water longer, you will have to use both arms and legs. You will also have to maintain your head up and make your hand in motion or in a horizontal way. Read more on http://www.wikihow.com/Tread-Water and http://www.ehow.com/how_2074950_tread-water.html.
gotta get into a rhythm and be physically fit. when i did it, waaay back when, i met my treading time by just focusing on not spending extra effort. control the breathing. make each motion count.