Yes but the mass doesn&#x27;t effect the volume of water displaced if you put in a hollow 10 cubic meter steel cube into water or a solid 10 cubic meter steel cube they&#x27;ll both still displace the same amount of water which is 10 cubic meters.<p>BTW the density of the sub is also for the most part pretty much equal to the density of water.<p>The only times where it&#x27;s going to be either greater or lesser than water is when it&#x27;s doing a static dive or fast ascent.<p>When the sub does it&#x27;s initial dive and takes on water into it&#x27;s buoyancy tanks it becomes about the average density of salt sea water once that is achieved it can use it&#x27;s diving planes (foreplanes) to adjust it&#x27;s depth.