navigatable

navigate +‎ -able.

navigatable (comparative more navigatable, superlative most navigatable)

1. Navigable
   • 1992, Peter Sammartino and William Roberts, Sicily: An Informal History, page 45

     Rivers were made navigatable, irrigation was improved, and the use of hydraulics was greatly increased.

   • 1998, Flexible Query Answering Systems, page 83:

     The second is that it has potentials for information exploration, because the displayed network is navigatable.

   • 2008, Michael R. Ash, Of Faith and Reason, page 67:

     The following year, Heyerdahl tried again—this time having learned from his mistakes—and the Ra II was built by the South American Aymara Indians from Lake Titicaca (the world's highest navigatable lake).

   • 2008, Euro-Par 2007 Workshops: Parallel Processing, page 72:

     Key characteristics of the Web are that it is simple to understand and use, deeply integrated in the user's desktop and working practices, navigatable through linking, loosely coupled and has unparalleled support in terms of tools and support.

The word navigable is the one found in other dictionaries, but it is possible that navigatable is a new coinage rather than an error.