As light goes from air to another medium (salt water in this case) it gets bent by the angle of refraction between the two mediums. In order for the light to be magnified, the water at the surface would have to form in a way as to focus the rays. You aren't going to increase the amount of photons as that is set by the bulb, but it could increase the intensities in specific spots. I doubt it would increase concentrations in specific areas by that much.
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