The Submarine part 3

1. To make it have negative buoyancy, we  (my partner and I) filled it with water, and it sank to the bottom. The more mass, the more dense.
2. The next move was to make it stay at neutral buoyancy. To do this, we emptied out some water, and also added some air using the tube (we couldn't use or body to touch the submarine) to make it a little less dense and a little less mass.
3. To make it have positive buoyancy, we added the most amount of air, and emptied out most of the water. It had very little mass, making it less dense, making it float.