Put some Bach Rescue Remedy in the water bowl for a while. I swear by the stuff. If you have multiple dogs, it won't hurt anyone being in the water. Dogs have more feelings than a lot of ppl give them credit for.
Give him some extra loving and talk to him. I always talk to my dogs and picture in my head what I'm talking about.
The one thing that comes to mind, I had buff dogs that were all related and a couple of partis that were rescues who stayed. Buffy Love was the dam of my litter. The last two buffs left were her and her one son, Flash. I wondered how Flash would make out as the last buff, because they always liked laying together. The parti's really are more independent and won't lay snuggled together.
We got our RV and our first trip out, we went to visit friends who have cockers too. I will never forget - Our dogs were in their back yard and their dogs came out of the house - they have two buffs and a chocolate. When Flash saw Tizzy his head snapped around like someone had slapped him and the little old man took off at a run for Tizzy. I think at first glance he thought it was his mom. Once he got closer he realized it wasn't her, but he always hung with Tizzy when we got together.