Thanks guys. Yes, floating algae are procedural, just taking the water mask, inverting and adjusting, warp a bit, breakup by PF and colorize. I wondered if it needed some displacement, but haven't done so far.
The moats were first 10m wide, but the client (museum archaeologist) decided to use existing digs' data and make them 6m. I was thinking the same as you, how would it stop an intruder? Even if deep, they might have their swimming licence. Maybe it was more of a psychological barrier, which made the inhabitants feel safe.
The prickly shrub was a second deterrence, but there was the walkway, how else would the inhabitants reach their tower?
But perhaps the front bridge should be a little larger (while wood was scarce here in the boggy and low North of Holland, so it's all disputable).