Sure, the water might look fresh and clean, but there may be millions of invisible critters tumbling around in it.   Thermal treatment of water involves cooking the little buggers to death.   Boiling water is considered 100 percent effective against protozoan cysts, bacteria and viruses.

You should bring the water to a rolling boil and keep it there for 1 minute for every 1,000 feet in elevation from sea level.   Boiling is simple, effective, and inexpensive way to treat your water supply. But, there are some drawbacks:

• Takes time to boil and then cool water
• Does not actually remove particles from water, just kills organisms
• Consumes fuel supply

If you don't mind dirty, flat, safe water, then its fine to drink it right after boiling. But, if you're like this dude, you might want to run it through a filter after boiling to strain out dirt, cysts, and at least some of the dead thingies. At least it will look cleaner before drinking it.