Bay

I am attempting to put up a good neighbor fence using 6x6 in cedar post and ran into a water problem. . When I dug my post holes to the frost level they filled with water to about 10 inches below the ground level. Incidently, I run into clay type soil after 2 feet (I believe that it is at the 2 foot level where the water seeps down into the post hole). I understand that I could fill it with dry quickmix cement that would eventually displace the water. Am I wrong in thinking that putting a layer of gravel down does nothing for drainage. If so, what should my concerns be with wicking and wood rot? Also should I use Sonatubes?