That’s the normal behaviour of the glass shader, which uses the fresnel function to blend a refract shader with a glossy shader; where light will reflect more at glacing surfaces, and refract at facing surfaces.
You can however create a new glass shader, mixing the refraction and the glossy by just a fraction of the fresnel, reducing the amount of the reflections produced.
Ace Dragon is right! If the normals are pointing in the inside direction, the IOR of the fresnel function is inverted, and Cycles understands this as if the first medium has an higher IOR than the second medium. This makes the water to look like if it is seen from underwater.