I just think that the problem is that the river is huge, fast moving and with divers reporting 3ft visibility . Without finding a body the police can not definitively say that Ariel entered the water but continuing a winter water search is just not practical. Even if the search teams had unlimited resources and skilled manpower, the search area is just too vast to be feasible.
In the absence of a body in the water, I think the police have to focus their efforts on other lines of enquiry even though the most logical, most precedented, most evidence-driven scenario is that the poor boy has drowned. I hope nature will be kind and reveal an answer in the waters soon because the parent's heart-break and desperate search for answers is almost unbearable to see. I do however also believe we should keep hope alive and not stop searching and exploring all possible scenarios... if I were the parent, I know I would never give up.