gulliBell
The reason that popping the floats won't work is that the aircraft is lying under 40 metres of water. The air pressure required to inflate a float at that depth is four times that at the surface, so the volume of gas required to just provide bouyancy at depth is four times greater that that required at the surface due to compression effects. The floats would burst on the way up in all likelyhood.
The standard method of recovery is to use open ended bags that are filled with just sufficient air to supply bouyancy. The volume of gas in the bags is adjusted by divers as the object is brought to the surface to strictly control the rate of ascent. An uncontrolled rise to the surface would be dangerous to personnel in the water, surface recovery vessels and risks further damaging or losing the object being recovered.
Bouyancy bags have been used for centuries as a way of recovering heavy valuable objects such as bronze cannon from the sea, so the methods are well understood even if they seem a bit low tech for the modern era of remotely controlled submarines.