Building a wood fence in yard with a high water table?

coat the posts to depth with a product called "Black Jack", it's roofing tar. let that set. dig down about 30 inches and place an empty 5 gallon container at the bottom then fill 3/4 with concrete. place your post in the concrete and rope it off or use 2x4s to bring it level. add concrete to fill the container. repeat for each post. after they're set and before you bury them, coat the top of each concrete filled container with the black jack. 5 gallons of concrete may seem like overkill - but when the wind blows (in addition to your high water table) you'll be glad you got them.