Perversely, Low Water is the highest tarn on the Old Man of Coniston, at ~545 m asl.
The fairly clear water looked very inviting, unlike the steep path ~250 m (vertically) down to it. I never like descents, and this one was to be particularly awkward, as the surface was mainly loose slate.
In hindsight, I might recommend climbing the Old Man via this steep path, and descending the gentler route we'd climbed.