Decking posts in boggy ground

[andyn210766]

I am about to build some decking (roughly 4.5M square and around 15cm high) at the end of my garden. The land there can get rather boggy so I am concerned to avoid the wood rotting prematurely!

There is varying advice about the posts: either rest on slabs or put posts into concrete. I am inclined to put the corner posts 2 foot into the ground and sorround with concrete; the other posts can simply rest on slabs or breeze blocks.

1) I am interested to have comments on this approach
2) Please can somebody advise how I can best waterproof my posts?