Dumb Question - Sprung Bowline?
 

On a new acquisition (a Southcoast 22) there is in the bows, a faucet
like handle,
which screws off to reveal a rubber bung and a sprung line which is
perhaps 1/4 in diameter and perhaps 20 ft long.
This line seems too slender to be a painter.
And it retracts. What is it for?

Thanks in advance.

Brian Whatcott Altus OK