Sailing from St Marys to St Agnes the sea surface was especially reflective. I've always thought of this as a "glassy sea" from the Biblical quotation. I was thinking about why it is so reflective. One possible answer is the the foreground. The motion of the boat through the waves mixes air into the water creating the white water. This does not offer specular reflection. There are too many surfaces in the bubbles which reflect light in all directions - a scattering effect giving the white colour. This is diffuse reflection. Any disturbance of the water by wind will give this and remove the specular "glassy" effect.
