A tip I would pass on is to attach treated 2x4s to the posts with galvanized lag bolts just above the buckets. Once you attach your joists, you can move the 2x4s into place for X bracing above the water line then cut off the excess. Helps the stability a lot. I have built several docks this way and they are all standing and in good shape even the ones that I built 15 plus years ago. The piers that run off of the deck are 4 feet wide and have a 2x4 underneath running lengthwise for extra strength. Remember to use scraps for additional supports for the joists. Always attach a foot to the supports.