I sometimes like to go out surfing as a form of relaxation 
Me too, I like surfing, which is a surface water sport 
Do you know who invented surfing?
It is believed that the native peoples of the Pacific, for instance, surfed waves on alaia, so they may have invented it.
Wow, what did they use as their boards?
They may have used paipo, and other such craft, and surfed so on their belly and knees.
Cool. When did surfing become a part of popular culture? 
In modern times, surfing means that surfer rides a wave standing up on a surfboard, around the 18th century.