A Polliwog or "Wog" is a sailor who has not crossed the equator. Crossing the equator invokes the mariner's ritual of turning Polliwogs into Shellbacks or "Sons of Neptune." A sailor that crosses that equator at the International Date Line becomes a Golden Shellback. This ancient ritual is observed by navies all around the world.

The "Crossing the Line" ceremony commemorates a sailor's first crossing of the equator, Latitude 00000. This maritime rite of initiation has its origins in veteran sailors testing their new shipmates to ensure they were capable of handling long harsh times at sea during the era of sail.

The eve of the equatorial crossing is called Wog Day and, as with many other night-before rituals, is a mild type of reversal of the day to come. Wogs-all of the uninitiated-are allowed to capture and interrogate any Shellbacks they can find (e.g., tying them up, cracking eggs or pouring aftershave lotion on their heads). The Wogs, however, are made very aware of the fact that it will be much harder on them if they do anything like this.

The highest ranking seamen officiate a ceremony during which the Polliwogs undergo a number of increasingly abhorrent rituals, chiefly contrived to entertain the Shellbacks. During the ceremony, these high ranking seamen characterize King Neptune escorted by his Royal Court, typically including his first assistant and scribe Davy (Davey) Jones (commander of all the evil spirits of the deep), her Highness Amphitrite (goddess of the sea and the wife of Poseidon) and other various dignitaries.