Buoyancy is the force that water tries to push up an object. For example, this is partially why a large, heavy object like a ship can float and in order to determine whether the object will sink or float you must first determine the weight of the water displaced. The weight of the water displaced is equal to the buoyant force pushing the object up. And next is density. Density is the relationship between the weight of a substance and its size and It's more dense it has a greater density. How to calculate density is mass ÷ volume. Mass is measure of the amount of matter that makes up an object and the mass of an object does not change when the location of the object change, so mass is constant. Volume is the amount of space that a mass takes up. Stability is when something is not likely to change or move. In my boat design was I was careful of the balance. I put a column on each side and gave a sense of stability.