With all that reserve buoyancy, its made for lifting something heavy. I don't think those are tanks
of any sort. There is cable winch
on the top.
The only thing I can guess is that it may be a box core
. A box core
is something that takes benthic (bottom) samples for research
. The large amount of reserve buoyancy would help to break the suction and to lift
the weight of the sample out of the water
. No idea what it might be otherwise.