I have a PT render going on 20 threads that's now at 37 hours and only 16%. I'm sure there are settings that are off, but even from the get go adding the water plane, without reflections for water on rocks near it, and rock ambient reflection, was taking forever to render at 0.5 AA 2. I thought i'd give the server a try with a larger PT render at MPD 0.7 AA 8 (for noise in darkness) and I'm not sure these times are desirable.
I feel there may be issues with light calculation in the cave with reflections and water. I can send the TGD via email. For example, when the water is added, things get VERY dark in the interior, which is odd since you'd think the plane reflection surface would actually provide ambient light, as well as reflected direct light (like how those shore caves in Oregon in Canon Beach area). Without the plane, and non-reflective light surfaces, things are brighter by a pretty large factor.