Crossing the Equator by sea remains a rite of passage. Unlike flying over it in a few hours, a ship takes days to approach the line. The ceremony—silly as it may be—connects you to centuries of sailors who crossed unknown oceans under sail.

If you’ve ever booked a cruise that sails from the Northern Hemisphere to the Southern Hemisphere (or vice versa), you may have noticed a peculiar item in your pre-cruise documents or onboard activities: the Crossing the Equator Ceremony .

And if you complete the voyage, you might just walk away with one of the most unique souvenirs in travel—the .

But what exactly is this certificate? Is it real? And do you have to kiss a fish to get one? Let’s dive in. A Crossing the Equator Certificate is an unofficial (but highly cherished) document given to passengers and crew members who cross the 0° latitude line —the Equator—by sea.

So next time you book an (think: Ecuador to Chile, or Indonesia to Kenya), pack your sense of humor. King Neptune is waiting. Have you ever crossed the Equator by ship? Did you get the certificate—and did you have to kiss a fish? Share your story in the comments below!