OK I found the underwater runtime. I have to do some work to use it. Upon loading the scene into PP2014, it changed the names of my props, adding _1 to them all. This messed up the script which expected names like "WaterPlane", not "WaterPlane_1".

I'm improving some of the materials. Here's a demo.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)