At the risk of sounding like a wise guy, don't shoot directly into the sun. What you are experiencing is sun flare. It can be caused by tiny specks of dust or imperfections on or in the lens, or reflections off the sides of the lens barrel. By using a CPL Filter or Neutral Density Filter, you can reduce the amount of sun flare, but probably won't eliminate it. That would have to be done in post processing.
When you do shoot sun shots, try not to shoot directly at the sun, but from an angle. This way the flare might just get out of the view, or close enough to the edge to crop out. Or wait until the sun is partially hidden in the view, then it won't be as intense a light source. I sometimes use trees to partially block the sun to reduce the amount of flare, but when you're at the beach, that can be difficult to do. Also, by setting a faster shutter speed, you can reduce the amount of light hitting the sensor to reduce the sun flares, then brighten the dark shadow areas in post processing. Not ideal, but maybe worth a try.
Steve M.
