The Scottish SPCA are now appealing to help find the culprit, after the animal’s body was discovered tied to a rock in the sea.
Inspector Emma Phillips said: “A member of the public came across the dog’s body by the Firth of Forth next to Cockenzie Power Station.
“The dog had string tied around its neck which was attached to a rock. The person responsible would only have been able to tie the dog up at low tide which leads us to believe they may have intended to drown the dog. Where the dog was found is also relatively remote.
“Due to exposure to the water, the body was so badly decomposed we cannot identify the breed or age of the dog. We also cannot be sure how long the dog was tied up or the exact cause of death, though it is likely to have drowned.
“This is a particularly disturbing case and it seems this poor dog was subjected to a horrific death which would have caused immense distress.
“We are urging anyone with any information to contact our animal helpline on 03000 999 999.”