Apples and oranges.
We are all fully aware of what the real estate tax values are for an inland home compared to what they are at water front property that has the ability to build a deep water slip. We are talking exponential values here.
But the tax rate or "mil rate" is the same per thousand of assessed value so they are really being taxed the same. One home is more valuable in FMV than another due only to location or proximity value.. For example we pay about $19.00 per thousand in property tax. So does our neighbor who is across the street and "technically" on the water. She pays the same mil rate we do just that her home is worth more so she pays more in taxes..
Let us not even begin to dig into the values that increase property tax when a structure such as a dock is built.
When we built our dock in Harpswell (actually got permitted to rebuild a decrepit and condemned structure) it added nothing to the property tax bill as the town did not feel it really changed our property's "value" as it was already waterfront and the land was valued accordingly by location. I am sure that in some states a dock does add FMV but the mil rate would be the same per thousand of assessed value as any other home. Most states have laws that stipulate how property taxes are levied and the vast majority are on assessed valuations in relation to FMV. A mil rate is then applied usually on a "per thousand" basis. California and some others do it differently but here in the NE most use the method I describe.
Here in Maine they tax the structure value, land value and outbuildings. In Maine there are no "adders" to calculate docks that I know of as it does not qualify as an outbuilding, structure or land.. Two summers ago our neighbors built a dock to the tune of 285K in cost. I just looked up their property tax bill and don't see that it changed at all from three years ago. That said different states likely have different ways of valuing waterfront property.
Then you have the costs of building the actual dock. In some cases, more than the price of a modest home.
Docks are ungodly expensive to build these days. While expensive to build they are not usually taxed at anywhere near the cost to build them, if at all, at least here in Maine... When I built our barn it added $1200.00 to our overall property value but cost far more than that to build.
Figuring mil rates is complex and all we can say is that waterfront property will always be worth more than inland unless your house is about to erode off a cliff or barrier island. Houses in prime neighborhoods or prime "locations" will also have a higher assessed value even for the same physical size lot and structure. Put our house/lot out in Westbrook, ME and we're paying about 1/3 what we pay to be in Cumberland, ME because the "location" is worth a lot less........
I still don't know what any of this has to do with moorings.....