Tip I picked up here on cpf: strap your headlamp to a clear water bottle, light shining in towards the water, makes a great tent lantern. Another one from CPF: nitecore makes diffuser attachments that fit on any 25mm or 40mm flashlight that most people seem to like. Others use diffuser film, or just semi-clear tape, as a diffuser.
Then, your possibilities are really wide open, finding a flashlight or headlamp with the low lumen modes and waterproof rating you want. I like the many moonlight modes on my Zebralights. I feel safe with my Zebralight flashlights and headlamps at least up to bathtub depth; any more than that, or if I were going to be pressing buttons repeatedly under water, and I would get a dedicated dive light. But, there are many, many more possibilities that meet your criteria.
