Bloat is very serious particularly in larger dogs and often the stomach gets twisted. When this happens, surgery is required to reposition the stomach. Without surgery a dog with a twisted stomach (gastric torsion and volvulus) will die.
Dogs with this condition often cough and try to vomit, but only watery fluid comes up. These dogs are not able to eat or drink. If you dog is able to eat when offered a tasty treat, this is not the problem.
Other causes of a boated look are eating a lot and swallowing air.
If possible, get your dog to the vet as soon as possible.
Let me know if you have follow up questions.