I like to surf in my free time.
I do as well.  I normally sure in the ocean, but sometimes I surf in rivers
Do you have to be standing on the board while riding a wave to be considered surfing?
Not at all.  A lot of people prefer body boarding, which you can do by laying on the board or just dropping down to one knee
Yes, i'm new to surfing, so I only surf lying down. What can you tell me about kite surfing?
There are a bunch of different styles.  There is freestyle, speed, course racing, among others.  I really enjoy it, but have only done it a couple of times.
What is the largest wave that a surfer has ridden?
I am not sure how big it was, but Garret McNamara broke the record.  His nickname is GMAC.
What are the origins of surfing?
It can actually be traced back to the Polynesians.  Modern surfing can be traced back to Hawaii