Floating and sinking might be common phenomena, encountered on a daily basis, but still represent conceptually complex scientific topics. Research has shown that most students have certain experiences and their own "theories" that explain why objects sink or float. Unfortunately, many of these "theories" are either misconceptions or are valid only under specific circumstances, lacking the generality of proper scientific explanations. Complete understanding of fundamental reasons behind objects' sinking or floating requires complex knowledge, including the analysis of the relationship between buoyancy and the force of gravity.