When your eyes water, the tears that you see are the very same ones that keep our eyes moist and comfortable, and wash out bits of dust and debris. Those basic tear secretions are produced in the conjunctiva, the membrane that coats the entire surface of the eye.
These basic secretions don't overflow like the tears associated with emotional crying. Those tears are produced by the lachrymal gland, located in the upper, outer corner of our eyelids.
Not only are they much more watery than basic tear secretions, but there are usually so many of them that they overflow and spill down your cheeks and drain through tiny ducts into your nose.
So why do eyes get puffy after crying?
It's because emotional tears are more watery, they're less salty than basic tear secretions and the tissue in your eye. So, through the process of osmosis, the water moves into the saltier ocular tissues, which makes them swell up.
And then there's all that furtive eye rubbing your "friend" does to hide his tears, which inflames his eyes even further. Still, even though it looks bad, the puffiness and irritation will eventually go away.