To me, the dock height should always be as low as possible and practical. Ultimately, the dock framing itself will determine just how low this will be. Even tho it is all PT lumber, I prefer to keep only the 6x6 supports submerged; not the framing. In our case, I decided to keep the framing members 6" above normal pool height. We will have enough water surface to be concerned for waves on windy days, so I seleceted 6" as a practical height above pool. More importantly, when we get a hard freeze at normal pool, the shifting ice will have less leverage if I keep it off of the framing members.
So, in the end, my final walking surface for the docks will be 20.5" above pool and the deck (at the end of one of the docks) will wind up at 28". No, to me this is not ideal. It's kinda high, but that's the way it is. As mentioned above, the higher docks do have an advantage for boat entry/exit. We plan on a 18' or 20' pontoon party barge in the future. I expect that as our knees, legs, and eyesight get older, we will look back and smile, reflecting on the wisdom of building the docks and deck at a higher elevation.
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All the bottom ledger framing members for both the dock and the deck are set at the same horizontal plane; 6" above normal pool.