The root cause is buoyancy. For a surfboard, the values of buoyancy and gravity determine that the surfboard will not sink.
There are two reasons for buoyancy:
1. The material density of the surfboard itself is lower than that of water, and the buoyancy caused by its submerged part under the water surface can counteract gravity.
2. The shape of the surfboard determines that it has a larger volume of water to drain (which is related to the bottom area and slight curling at the edges), resulting in greater buoyancy that can counteract gravity. If the bottom area of a surfboard is very small, there is no chance of obtaining sufficient buoyancy.
Pressure is only a reflection of the interaction effect between the surfboard and seawater, and does not determine the sinking and floating of objects. The force of water on the surfboard is buoyancy rather than support. If it is supporting force, it is related to the magnitude of pressure.
