Excellent! According to the Archimedean Principle a body within a gas or a liquid substance is affected by buoyancy. In any case, this buoyancy depends on the volume of the body. The wooden chunk has got a greater volume than the chunk of iron, therefore the buoyancy on the wooden chunk is greater.

Whereas the weight force (yellow arrow) is compensated by the buoyancy (red arrow) in case of the wooden chunk, in case of the iron chunk the weight force is greater than the buoyancy.