This chapter focuses on the production, storage, disposal and finding of waste material, such as “shot” or ballast—matter that settles to the seabed as part of submersible dives. Taking on this example, alongside a discussion of the politics of anthropogenic waste at depth, it both widens the remit of how we might think of oceanic sediment and in doing so opens discussion of the matter that comes to shape a seabed of exclusion and discard. The chapter hones in on contemporary and historical dives to Challenger Deep in the Mariana Trench, the deepest known area of seafloor in the world, considering the material evidence of “frontier exploration” left as waste in perpetuity on the seabed, while also attending to human waste disposal politics, and the stratification of access to seabed (where wealth and gender have historically acted as barriers to partaking in expeditions). Together, it interrogates how narratives of exploration, technology and masculinity are materialised through sedimentary relations.