Hello, I was attending a physics discussion on fluid dynamics (fairly basics concepts) and the classic buoyancy demo came up. (A test tube is inverted and allowed to be filled with enough water to float with the volume of air trapped in the tube, the test tube is inside a larger bottle which is then squeezed, compressing the gas and allowing the tube to sink) The Argument I became engaged in was the manner in which the sinking was occurring. I argued that the gas was compressed, causing a lower volume of gas, and thus a smaller amount of buoyant force. This then caused the test tube to sink. The teachers argument was that the amount of water displaced remained the same, however the density of the gas increased, causing the test tube to sink. The same demo was performed using a non-rigid container filled in a similar manner with a gas, and in this case it was agreed that the compresion of the gas was responsible. Was I right?