As mentioned, you can use Polarizing filters to reduce reflections and glare on water and other surfaces, such as foliage.
For example, compare the photographs of the fern fronds.
The fronds are more whitish in the top photograph.
The white that you're seeing is glare.
The glare is reduced by the Polarizing filter in the bottom photograph.
The fern fronds are more green because the glare has been reduced.