I think surfing looks like a lot of fun but I would be a little worried about sharks.
Yes, i like it surfing too, native peoples of the Pacific, for instance, surfed waves on alaia, paipo, and other such craft
Is it difficult to surf, does it require a lot of balance or skill?
Well surfers can also utilize artificial waves such as those from boat wakes, i think when you learn it its like learning to ride a bike, you cant forget it
I wonder if it is similar to water skiing? 
Its a water sport in which an individual is pulled behind a boat, so i think that its a department of surfing :D, and can still be called that way :D
Is the equipment like surfboards complicated or expensive?
Surfboard
A surfboard is an elongated platform used in surfing. Surfboards are relatively light, but are strong enough to support an individual standing on them while riding an ocean wave. They were invented in ancient Hawaii, where they were known as "papa he'e nalu" in the Hawaiian language, they were usually made of wood from local trees, such as koa, and were often over in length and extremely heavy. Major advances over the years include the addition of one or more fins (skegs) on the bottom rear
refers to the act of riding a wave with a board, regardless of the stance used. There are several types of boards. The native peoples of the Pacific, for instance, surfed waves on alaia, paipo, and other such craft, and did so on their belly and knees. The modern-day definition of surfing, however, most often refers to a surfer riding a wave standing up on a surfboard; this is also referred to as stand-up surfing.
Another prominent form of surfing is body