Sailingdog is right
Neutral Buoyancy means it will stay at a given depth (even if right at the surface). Negative Buoyancy means it will sink (at that depth).
By this strict definition, I'd say the "boat" actually has a slight Positive Buoyancy. If it truely had "Zero Buoyancy," no part of it would be above the surface of the water...not even the mast.
Just my thoughts...
Skipper, J/36 "Zero Tolerance"