From the Breakwater Marina to the Army Museum and back is about 4km and its as pleasant as it gets with good shade cover and spectacular views of Magnetic Island.
For the kids there is a free water park with all sorts of water sprays, showery things and water tipping doodars. For those not keen on getting wet there are many places to just sit and practice omphaloskepsis or of course drink coffee and chat.
All in all, a good place for a morning caffeine hit or a lazy afternoon people watching.