I know most people are pro concrete (or equivalent) but I think it helps wood rot. Crushed rock/gravel is a better post base.
And I worry that an H brace on posts that are shallow sunk will not hold up well.
Polytape is the most visible, so a great choice for horses.. .
Might be perfect for ducks for the same reason. You can get it in a few different colors too.
These 2 pages (yes for a specific brand... but ignore the brand/marketing) have a good explanation as to the different wire and...
For wood corner posts that can't go in deep, google Rock Jack.
That is what you want.
OR, use this handy dandy, very long but DETAILED fence building guide with lots of drawings to show you how to do it. And it does cover several different "can't dig my posts deep" choices... including rock...