Thanks guys.
Ulco, it's cropped. I was going with the wider shot but never got happy with the framing, and things became too far away to become hero, so went for a 100 mm lens to pull things together in frame. The render problem was the seaweed had reflective shader with RT unintentionally switched on, so after seeing that half the frame had rendered in 3 hours I felt confident that the render would pop during the day Monday.
