Caustics in 3.60.02

ledisnomad

I'm trying to get caustics working for a swimming pool. I just downloaded V-Ray 3.60.02 and I'm using SketchUp Pro 2018.

I can get caustics working with a drinking glass and a spot light,
Drinking glass, caustics from spot light

but the I was hoping to get it working with displaced water and the Sun.
Pool, sun only
Pool, underwater, sun only

There are a lot of tuts around the web, but none seem to address it with VR3.6 for SU and so even trying to match settings ("check or uncheck the Affects Shadows"... for the material? For the Sun?) is confusing as an infrequent V-Ray user.

Can anybody help?

Packaged Skp+V-Ray