There was another thread somewhere the indicated that in order to build naval units an adjacent body of water must have a certain number of water tiles. Two bodies of water linked by city or fort do not change this so a city on an inland lake, even if it has access to a larger body of water via a channel, cannot contribute to naval production.
An inland lake (not coast) CANNOT have resources and is guaranteed to be smaller than the specified threshold and thus your city cannot build naval units (and would have no need for a workboat)
The wonders that require water apparently do not care about the size of said water body, which would be a questionable design decision (as is, in my opinion, not considering the aforementioned "channels" in calculating total accessible water tiles) but not inherently a bug (albeit an advantageous one)