Here in St Petersburg Florida we have lots of boaters, a number that's increasing each year, as in the whole state of Florida. At the same time, marina space where you can rent a slip for your boat in decreasing. Many marina owners want to sell the slips, rather than rent them - thus dockominiums and rackominiums. The best use of waterfront land has also been for condominium projects rather than marinas.
Slips here in St Petersburg and Pinellas County are selling for $200,000 and more. That could be 25% to 33% of the price for a waterfront home WITH a dock.
In other parts of the country, a dock can add up to $1 Million to the price of a waterfront home.
In the northeast, especially a bit inland , having a dock means you're right on the water, and that's a lot more money than in many Florida cities that have more water oriented properties. In cities like Annapolis, Maryland, being on the Chesapeake Bay or even the Severn River (it leads to the Bay) add a bunch to a property's value. Here in the DC area, many waterfront properties are on the Potomac River, which is not real navigable above Georgetown. And while there is added value to being on the water, most of the nicer condos are smack dab on a flood plane, and their condo fees are exorbitant because their garages full of real expensive cars flood every few years.
Any view of the Potomac probably triples the value of a lot. Many older homes are bulldozed for major architectural statements.