water around spark plug....WHY???

Need some more information, year model primarily. Any mods?

If it's an NPI or early PI headed car, the intake manifold crossover may have cracked. Or the intake manifold gasket could have gone bad, although I've never heard of this and don't know why it would.

It is possible that the head gasket is blown, but it is very rare on these 4.6 cars. I know some guys pushing 15+ pounds of boost and not blowing head gaskets.

Simple question: Where is the water coming from?

If you cleaned up the cylinder head on the driver's side all spiffy-clean and went back a week later, what would you see? Any evidence of coolant trails? Oil leaks? Or is the top of the head dry but the plug well full of oil/water again? Does it happen if the car is soaked with rain or a carwash? Any water ingressing through the hood scoop (e.g.)?

It's suspicious that it's only one plug involved. What does the firing tip look like compared to the other cylinders? Is the car losing coolant or is water mixing in the oil (milky dipstick, for example)?

Are you sure its water and not Gas/oil blowpass? I'm pretty sure the number 6 plug is the one I blew out of the head once before myself...