This is opportunistic and free for everyone to use. For a big number of use cases you need licensed spectrum to ensure some minimum standards of communication. Imagine what happens when a lot of WiFi access points are in the same small neighborhood.
However I've seen that there is proprietary protocol symphonylink from LinkLabs, that uses LoRa. They claim that it allows for having every frame ACKed, even bulk data uplink (OTA firmware upgrades). If so, I would tend to pick such technology for pond water telemetry.
But wouldn’t it work for this use case he had?
I believe that in the long term and as the number of devices per unit of area increases, licensed technologies will be the only viable option.