Roger Chartier intro video

A sea shanty or chanty is a work song.
In the same way Chinese coolies had work songs and the way  the African slaves of the south had work songs so too did the sailors and whaling men and dockhands of the era.                          

 The tradition spanned many years. The first shanties found were in early texts  written by a monk describing a chant  sung to the job of work done by sailors on his trip to the Holy land from England in the 1400's(?) It was many moons ago.. The 1700's and 1800's brought us the most memorable shanties.
Most that we hear came from England Ireland and USA although every maritime country had them. I was being rowed on a sampan sort of boat in Suzhou China and the woman was singing a Chinese language Sea Shanty!

Here is the windlass of the Charles E. Morgan

A capstan shanty: used when working the large   vertical drum with a mushroom shape on the top which had holes for the bars that were inserted to push the capstan around and around, So, they worked in a circle. They would stamp on deck at times with the rhythm, therefore, "stamp & go Shanties".
That, for one thing, wound up the anchor chain. 
Halyard shanty:   was used with a grunt or a stressed  word  at a part of the song to accentuate the  coordinated pull. The work couldn't be done if not in a timed, concerted effort. The halyard raised the yard to which the sails were  hung. Despite the advantage of block and tackle, some could weigh over a ton.   
Short Drag Shanty   For tough jobs where men worked shorter distances such as raising a masthead or trimming sails.

Here's Roger Chartier on the windlass.

Windlass and Pumping Shanties  A windlass is shaped like a barrel on it's side, horizontally that is, with handles at either end.  Handles were worked up and down. 

 On pump brakes (downtown pumps) an eye splice on the end of a rope was fitted over the end of a handle so that several men could work on it together.
This was called a bell rope. The sailors pulled this in teams.
The way shanties are played today are sometimes in a  fun, yahoo sort of a way. That is not the way the sailors etc. of the time  used them to do a slower more laborious job of work. Surely they did raise hell on occasion. We shanty singers are not working when we sing them,  we are both presenting a piece of history and oft times  having fun.  So the presentation  again, has changed just a little.