True, Iron is not buoyant in water because it has a greater density than water.
The buoyancy of an object in water has a lot to do with its density. The buoyancy of an object in water is proportional the difference between the density of the object and the density of water.
If the object is denser than water, the object will sink and not be buoyant in water. If the object is less dense than water, the object will float and be buoyant in water.
