Yes, if you dive and release Restube under water, the buoy pulls you up. It is connected to the safety line with the belt. The same amount of gas always flows into the buoy, which means that at sea level and room temperature it is well filled. When you dive, the ambient pressure increases by one bar for every 10 m of water depth, and at the same time the buoyancy force is reduced in depth, as the gas is compressed. This results in the following buoyancy depending on the depth:
0m depth = 1 bar = full buoyancy = 75N = 7.5kg
10m depth = 2 bar = half buoyancy = 37.5N = 3.75 kg
20m depth = 3 bar = third buoyancy = 25N = 2.5 kg
30m depth = 4 bar = quarter buoyancy = 18.75N = 1.87 kg
40m depth = 5 bar = fifth buoyancy = 15 N = 1.5 kg
As soon as you get higher again, the resulting buoyancy of the buoy increases until it is fully available again at 0m/sea level.