• The reason you can stand on a surfboard without sinking is because your force weight is spread out all over the board and this decreases pressure on the water, allowing you to float.
  

There is a certain way that a surfer must stand on his surfboard to avoid tipping or twisting. 

• Stringer - the thin piece of wood that runs down the middle of the surfboard. It is only about 1/8 inches thick but it is a great source or weight and strength.
  
• Center of gravity - on a surfboard, the center of gravity is located on the stringer, closer to the back of the board. This is because of the added weight at the back due to the fins.

The surfer has to position himself properly along the stringer.The surfer should have one foot near the front of the board and one foot near the back of the board. They should be on either side of the center of gravity of the board and they should both be placed along the stringer. When the surfer stands in this position, there should be no rotation, or torque.