From the Long Forgotten blog, a characteristically excellent and thorough going-over of the aborted plan to build the Haunted Mansion as a boat ride-through, much like Pirates of the Caribbean (which may have cannibalized some of the aborted watery Mansion plans).
That's . . . bad. Anyway, we've assigned Fred's light bulb moment to about 1964 or 1965 and concluded that it was probably a live option for some time. So what? Here's what: It means that the Haunted Mansion boat ride idea was born, lived, and died during the same time period that the Imagineers were hard at work on Pirates of the Caribbean. Walt had already decided by the end of 1963 that POTC would be a boat ride, with guests going down a waterfall and beyond the berm to a big show building. Coats and Davis and many others were knee deep in the POTC project in that format by 1965. If that is the historical context for Fred's Mansion idea, we may reasonably ask if any vestiges of the abandoned concept were incorporated into POTC. I think it's possible. Note that one of the very few things we know about concept artwork for this version of the HM is that it reminded one viewer of the Blue Bayou. Well, that artwork was done before the Blue Bayou was built.