The present invention relates to a buoyancy modification module 10 for a modular underwater vehicle, wherein said buoyancy modification module 10 has at least one first frame 20, wherein the frame 20 is designed to connect the buoyancy modification module 10 to other modules, wherein the buoyancy modification module 10 has at least one first pressure hull 30, wherein the first pressure hull 30 has at least one first flooding region 50 and at least one first dry region, wherein at least one first pump 40 is arranged in the first dry region, wherein the first pump 40 can pump water out of the surroundings or a neutral-buoyancy reservoir into the first flooding region 50 and out of the first flooding region 50 into the surroundings or a neutral-buoyancy reservoir.