Our submarine was able to go submerge under water, blow back up to the surface and hover with a great time in the final test. We were able to do this by controlling our DENSITY and BUOYANCY during the challenge. When Alex [my partner] blew through the tube and blew the balloon up it had a positive buoyancy and a low density. When he sucked the air out of the balloon the submarine sank to the bottom of the tank. This is negative buoyancy and a high density. He was then able to hover the submarine at around neutral buoyancy or close to a density level of one for that to work.According what Archimedes said, “Any object placed in a fluid displacements weight;an immersed object displaces its volume.” We use this method to built the submarine.