A lakeside journal can begin with a single view. Find an established place to pause and describe the water, the opposite shore and the nearest foreground. Keeping those three layers in mind makes a broad landscape easier to put into words.
Write down the conditions you experience rather than looking for a dramatic scene. Perhaps the surface appears smooth, perhaps reflections break into narrow bands, or perhaps reeds interrupt the view. Each version belongs in the record.
Try a small sketch with only five lines. The aim is to remember the arrangement of the scene, not to produce a finished drawing. Add a sentence about the sounds that a photograph would leave out.
Before leaving, note one detail you would like to revisit. That question provides a gentle starting point next time and turns a pleasant pause into an ongoing conversation with a familiar shore.