Canyoning anchor rope setup - Joels releasable retrievable system - quick overview (6 minutes) 

This was a dry pitch with plenty of rope so not going to lose that biner. I loaned my Hannibal to the lady on the background so was using a Gi-Gi as a descender. But yeah the risk is there if the rope length is set in deep water. Using a canyoning draw (two lockers connected with dog bone) is a way to prevent that from happening.

Nice self-review picking up the not-a-mule-but-a-half-hitch, I did notice that but really happy to see you point it out yourself! Re: the "biner block" where you used a clove-hitch, I have been teaching (in rock climbing) that we should close the system by clipping that carabiner back to the load line, making a "P" shape through the anchor and meaning that even if the biner-block slips somehow through the rings it doesn't result in a fall, and it doesn't affect the ability to retrieve. Sure... you'd have to use some imagination and pretend the ring happens to be more like a steel hula-hoop but you get the idea!. Is there anything in canyoning that speaks against this? Just interested.