Once the last unclaimed solid expanse on Earth, the ocean floor has become one of the most contested spaces in contemporary geopolitics. The data-imagery produced by technoscience serves as the ultimate tool for nations asserting sovereignty in this territorial race. This symposium gathers diverse perspectives on the ongoing expansionist drive on the seabed, drawing inspiration from Abissal——a film-article featuring the Portuguese modern odyssey on the ocean floor that serves as the symposium’s centerpiece. Aligned with modern ocean law, technoscience strives to render ocean depth visible to politics and territorializable for coastal states. However, the submerged prolongations and divisions it proffers are inherently political, as the images and knowledge it reveals are inseparable from the territorial regimes that commission them. Acting like an upward-facing mirror, the seabed divided by technoscience reflects humanity’s expansionist thirst back to the surface. Yet the conquered depths do more than merely reflect this impulse; they also diffract the abyssal politics above. This symposium introduces a critical and creative conversation on the territorialization of the deep-sea and its far-reaching reverberations——both within and beyond ocean space.