Pulled out this gnarly looking anchor from right in the middle of the canal junction before the CRT bridge operator came out and told me I wasn't allowed to magnet fish in the canal. After that I walked 100m down the towpath and pulled out all of this stuff:
First trip out with the massive Barbarian magnet and it's definitely better at sinking down into the mud, although I don't think I'll be doing full 20m casts with it without a lot more practice.
Steel fencing is common to use for bank soil retention.