Valid point. Although, maybe a remote controlled one could be made smaller or dive deeper and thus be less easy to detect. It could be made more solid through

Valid point. Although, maybe a remote controlled one could be made smaller or dive deeper and thus be less easy to detect. It could be made more solid through and through, thus be less likely to be crushed at lower depths, thus become smaller. Most of the space is probably due to life support and the driver being able to move around in it, and not to store the goods.