A very worthwhile discussion.
I don't know your local situation but there are two steel posts at my local which are very helpful.
They mark the shallowest part of the sand bar and were deliberately placed by an enterprising windsurfer.
I don't know of any one who has run into the posts but there were plenty of catapults prior to their installation through people running aground at low tide. They now serve as orientation for the location of the rest of the sandbar which is also useful for catapult prevention and speed runs.
Initially the posts had that orange webbing around them which made them very visible. The webbing is gone now and they can be hard to see from a distance in low light or late afternoon, but no one has run into the posts that I know of.
Increased visibility would be an advantage. An orange witch's hat over the top or a colourful float impaled on the top would be very useful for finding them from a distance.
My points - a post which marks shallow water is useful and less harmful than not knowing where the shallows are - hence navigation markers on waterways.
The more visible that post is the more useful it will be.
I hope that helps