BoyPete writes
I intend building a pergola type structure over my pond. I want to use a
covering for the top to create some shade. As the top will be level, I can't
use a waterproof material. I'd 'like' to use something more natural. Reed
matting perhaps? I wondered if the gardening community might advise?
Thanks

Think about access - whatever you use will need repairs at some time.
--
Kay