Day-1 Pollywogs against Shellbacks, Day-2 The Shellbacks get their Revenge! Good Times and Memories! I'm certain all they do now is give you a certificate for crossings. 

The Line Crossing Ceremony might just be the most interesting of today's naval traditions.

A Time-Honored Tradition

No one is really sure when or how the Line Crossing Ceremony, "Order of Neptune", came about. The ritual dates back at least 400 years in Western seafaring.

The ceremony observes a mariner's transformation from slimy Pollywog, a seaman who hasn't crossed the equator, to trusty Shellback, also called a Son or Daughter of Neptune. It was a way for sailors to be tested for their seaworthiness.

When a ship crosses the equator, King Neptune comes aboard to exercise authority over his domain and to judge charges brought against Pollywogs that they are only posing as sailors and haven't paid proper homage to the god of the sea.

High ranking members of the crew and those who have been Shellbacks the longest dress up in elaborate costume and each play the part of King Neptune's court. For instance, the ship's captain might play the part of King Neptune himself. What proceeds is a day of festivities, which builds camaraderie among the seafaring crew.