The arrow in the x-ray above is pointing to the fluid build up in the sinus cavity due to sinus infection.
The result of surfing in storm run off with a high bacteria content.
It should clear up in ten days or so without antibiotics and provided there is no re-exposure to the run off.
A neti pot can sometimes help re-leave the symptoms.
You can avoid the whole deal by staying out of the water for a few days.