Yes, since the density of air is less than the density of water, a buoyant object in air is buoyant in water. In any body of water that is exposed to the air, in fact, said object would escape the body of water entirely.
Air is more buoyant than water because air is less dense than water, and everything the thing that is less dense is always more buoyant than what is more dense than it.
When the density of the object is less than the density of the liquid or gas it is buoyant. For example, the density of wood is about 40 lb per cubic foot, while water is 62.4 lb per cubic foot, so...
That completely depends on the object's volume (which you have not mentioned).The buoyant force on it is equal to the weight of an equal volume of water.