Watch live: US Naval academy freshmen attempt to climb 21ft greasy pole in human pyramid

Watch live as members of the US Naval Academy's first year class attempt the annual climb of a granite obelisk coated in a thick layer of vegetable shortening in Annapolis, Maryland.

Every year, freshmen - known as "plebes" - form a human pyramid to attempt to climb a 21-foot pole to replace a "dixie cup" hat with an upperclassman's hat.

They work together to scale the Herndon Monument, named after Navy Commander William Lewis Herndon, who "possessed the qualities of discipline, teamwork and courage."

The rite of passage marks their graduation to Midshipmen 4th Class.

It took the "plebes" 2 hours 31 mins and 41 seconds to replace the cap last year.

The tradition first began in 1950, though it did not feature any grease - this was later introduced as upperclassmen apparently thought that the challenge was too easy, so began covering the structure in vegetable shortening.