To answer your initial question, yes the idea of "liveaboard" would need approval on all fronts
mentioned, i.e., Federal/State/County/City Zoning laws, submerged land owner's permission,
CG, and I'm sure Deed Restrictions would play a part as well.
To the "does the electric company bring power to the docks", that would more than likely
be a "no". There may even be utility easement issues at play if the power lines are all in
the front of the houses. Usually, in these underground utility developments, most of the
easements are in the front 10-15' of the property and the owner of said house is required
to take the power/water/gas/sewer/etc. onward to the home itself.
And finally, easement for access to these docks will come into play at some point. Sure,
"John Doe" may own the submerged land and even the docks, but he/she doesn't own the
property that would allow you to walk across land to get to them. Living aboard anywhere
is going to require you to be able to get off the boat at some point, so keep that in mind.
If it came to be that the dock behind my house belonged to someone else, I can assure
you that NO ONE would use it, because I'd deny access to it. Not many people would want
to dock their boat, then swim to the closest public access point to get off it.