■How to use a bucket

You can also use a bucket if you cannot prepare a lift bag.
However, these things do not have an exhaust valve, so buoyancy during ascent cannot be controlled.
As the air in the bucket expands as it approaches the water surface, if you use a bucket with a capacity that can give more buoyancy than the weight of the recovery object, you will not be able to control the ascent rate near the water surface.
Use a bucket with a volume that allows the target object to have a slight negative buoyancy even if the bucket is filled with air.