Sorry for the late reply. I just checked the file. I did not add a light. I only used a sky texture node set to 'Nishita' and used the default settings for the node. You can use it by going to the world tab. Make sure the surface is set to 'Background' and under 'Color' Select 'Sky Texture', Or go to the shader editor, set it from 'Object' to 'World' and add the node there. Make sure to add a 'Background' node if there isn't one already and set the strength to 1.