Cartesian Diver Explanation

In science, as part of our density unit, we did the cartesian diver experiment. Here is my explanation:

 When the diver is floating at the top of the bottle, it is positively buoyant, because it is floating. When we squeeze the bottle, we are decreasing the volume of the bottle, and increasing the mass of the diver. This is because the water is going into the diver, increasing the mass. The ballast to make the diver to make it sink was water, because the water is going into it to make it heavier. When the diver is in the middle of the bottle, it is neutrally buoyant, because it is just floating in the middle. So, squeezing the bottle slightly causes the diver to become neutrally buoyant. The diver is negatively buoyant when we squeeze the bottle hard, which makes it sink to the bottom. When we squeeze the bottle hard and water goes into the diver, the density of the diver must have turned to more than 1 g/cm3 because it is sinking. When the diver is at the very top, the density would be less than 1 g/cm3, because it is floating. The density would be around 1 g/cm3 when the diver is in the middle.