Our group (Akex, me, Jackson) did a awesome job of the Great Science 7 Density Challenge. The Instructions are: 1. the length of the apparatus must not exceed 40 cm in any dimension. 2. the apparatus can have no external force applied by hand(ex. push or pull) 3. The apparatus should descend and ascend using the principles of buoyancy and density. This may be achieved by controlling/adjusting air pressure with external tubing. 4. To successfully compete, the apparatus must be able to: a. float on the water's surface for 10 seconds. b. descend to the bottom of the sink/tank. c. ascend back to the surface and float for 10 seconds. d. hover between the water for 5 seconds. 4. the goal is to build an apparatus that can descend to the bottom of the tank and ascend back to the surface as quickly as possible (a time event). 6. a minimum of three classes will be given to design, build and, testing your apparatus. We hit 16.7 seconds for our score and we are Best in our class. I am very satisfied with my overall design because we successfully met all the challenges on the criteria sheet. When I blew the tube, the submarine is floating on the water because the air makes the buoyancy positive and makes the density less than 1 g/ml. When I sucked the tube, the air started to lose and the water comes inside the submarine, which makes the buoyancy become negative and the density is over 1g/ml. When I blocked the tube, the little amount of air and water was staying inside the submarine . That forms a neutral buoyancy and the density of 1mg/ml. I would change a little about our submarine if we are going to do this activity again. I would add more rocks on the bottom of the submarine because it can makes it sink faster and our hovering problem is the submarine sinks a little slow. But I am very proud of our overall result.