bucks and beaks, welcome to the forum.
I've built a number of floating piers. For my personal pond I used plastic 55 gal barrels. Never, ever again. You go thru all the work to get things just right and then one or more than one leaks even though the bungs were siliconed before screwing them in.
You can use 4x4 or better yet 4x6 posts on the shore, get the hinged specialty hardware from
Dock Builders Supply and build the dock using their floats. You won't ever have to worry about it coming apart. Fireishot and I built one recently at his place, we flipped the 10' x 20' section over 3 times and not one creak was heard from the wood.
Here, take a look at it. 5' wide walkways, I believe they are 16' long, the end is 10' x 20'. All anchored to the ground with four 4x6 posts.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=481370&page=20 
