King Neptune Ceremony
This is a traditional activity aboard a ship that crosses the equator. Based (very loosely based!) on an old sea-faring tradition, crew members who have not crossed the equator aboard ship previously "stand in" for everyone—passengers included—who are new to the equator-crossing experience. Of course, unless one is watching the ship's GPS position (which is easily done via the ship's in-room television) a passenger wouldn't know exactly when the ship crossed this invisible boundary, and our experience has been that the ship will schedule the event on a convenient sea day. If the ship will cross back on the return portion of the voyage, there will probably be only one ceremony, following the final crossover. The "slime" you see is an egg white/food-coloring mixture and the pool area is thoroughlly cleaned afterward, including draining and scrubbing the pool.
The event would usually be held at the outdoor aft pool, but rain forced this ceremony indoors to the Lido pool, which can be covered if it rains.
Our blog includes more King Neptune photos in the November 2012 South Pacific cruise.