Thanks for the hdr clarification guys.

Once I've worked out a good technique I will share it.

That first one was relatively straight forward... with just a flat sea plane.

Once introducing landscape, there a few more issues like, e.g. how high should the camera be, cropping up... (technically that question applies to the sea plane too of course)

...on that point, how high should the camera be, ideally, do folk reckon??

;-)