I think that is the problem with pigeon holing music to one category or another. Im my mind "Rock the Boat" is in no way disco, not even proto disco. If I had to categorize it I might call it soul or even pop. I've long considered Bee Gees - Jive Talkin’ to be the first disco type record (that I was aware of), but I'm sure that it's not. That record for me was a big departure in that groups style (and I didn't like it). Still even that record is not exactly what I would consider to be disco.
Anyway I think that it's time to pull out my 45 of Brother Jake and The Incinerators "Disco's In The Garbage". "All my disco records are deep inside a bin, let me open up the lid and throw more garbage in"!
Sorry if I'm offending anybody who actually likes disco, it was very polarizing at the time. The way it came in and overtook (dominated) all other forms of music fueled the extreme backlash against it.