Kimmy,
Get him to the vet!!! All of these symptoms are classic signs of parvo. The incubation period is 14 days and until he has had 3 shots of the vaccine he is not fully protected and even then it's not a guarentee. I've seen perfectly healthy adult dogs who are fully vaccinated come down with because the virus mutated and they got a different strain.

Even with the water, he is losing electolytes, so will probably need sub Q fluids.

Let us know!!

Molly