You'd better not open your eyes in the ocean when you don't wear the swimming goggles because there exists a lot of bacterium in the ocean. If the bacterium comes into your eyes, your eyes may get infected which may cause the eye disease. Thus, you'd better wear the swimming goggles. Then you can play as you like.
No, it's dangerous if you do that. As we all known, the salt concentration in the ocean is higher than that in your eyes. And the salt concentration in your eyes is about the same as the rest of your body fluids. That is to say, there is less water and more salt in the ocean water than in your body fluids, water would tend to leak out in to the ocean to equal the salt concentration on both sides, thus It can cause your body dehydrate and dry eyes. If you keep opening eyes in the ocean, the water would be absorbed into your eyeball that leads to blindness finally.
Of course not. As we all know, at present the water in the ocean are polluted seriously because of a surge of development .Moreover, the water in the ocean contains significant amounts of dissolved salts and bacterium which will do harm to our eyes. In that case, our eyes may be infected or we will get sore eyes. So I advise you to wear goggles and not to open your eyes in the ocean.