I built "Davy Jones' Locker" for Bricks by the Bay 2015.  This was definitely my longest diarama to date, as it took up the length of an entire conference table.  Among the interesting features are the bluish LED uplights that I placed along the base of the rock work.  The goal was to give a sense of looking underwater.  I used a large number of 1x2x5 transparent bricks mounted on edge with a white double cheese slope to give the impression of the waterline and surf above the underwater scene.