I try achieve this effect. Long reflection on the water. I tried to use actual sun lamp but I didn't get this effect. I achieve kinda this effect in another scene with ocean modifier and sun lamp but ocean modifier is heave on a system. I there any way to make this reflection with glossy plane. Maybe some distortion or another glass plane?
You could use a material similar to the following :
Here the 'sun' is an emissive sphere and a Bump node has been used on the plane to give the appearance of waves (from a Noise texture), using Fresnel to blend between Diffuse and Glossy. Be sure to keep a bit of Roughness to the Glossy shader (that's what causes the reflection to 'bleed' towards the viewer) and adjust the Diffuse shader to give a hint of color.