Why do these jet skis have ropes behind them?

[kayn]

Hey,

Just wondering why these skis have ropes behind them. (This screenshot was taken from a big wave surfing video)
https://gyazo.com/06ba6e37f733effa1f4c60ba1812da45

 

[Desert]

remove that from your signature you cunt

 

[kayn]

remove that from your signature you cunt

teehee