First of all, please check the water sensors (two metal points on the Deeper) on the bottom of Deeper casing, if they are in a good condition. They are responsible for activating the Deeper. You should clean them up with a rough sponge to remove any rust or other residue on it.
Afterward, you can check if it works by touching both of them (at the same time) with a wet finger - if you see a LED indication light up, seems that cleaning helped and the device will work in water. Alternatively, you can put the Deeper in the water and try to connect to it with your phone.
Otherwise, if aforementioned solution didn't help, please contact us at firstname.lastname@example.org or open a new ticket.