Well, sea water is sometimes very dirty and contains a lot of pollutants and chemical discharge, which would harm your eyes, leading to some red eyes, but that is not serious, you just need to get some eye drops to deal with your problem. But if the situation remains bad, just go to see a doctor.
Yes, it is normal for your eyes to get red after surfing. It is a sign of eye disease. Your eyes may get infection after the surfing. You could use some medical care to treat the redness. You could also use the eye drops to release your symptom. You'd better wash your eyes after the surfing. You should take care of the eyes very much.
Yes, it is normal to get red after surfing. Our eyes are easy to get infected or irritated by the outside world. When our eyes are irritated or infected, they will turn red. It is very common. During surfing, water has access to getting into your eyes and thus your eyes may be infected. So you don't need to worry too much about it. But you should wear goggles in order to protect your eyes well when you are surfing. You can use eyedrops to comfort your eyes. If you still feel uncomfortable and your eyes create extra tears, you should go to see a doctor.