The marine benthic biodiversity survey Investigating the IOT took place in the waters of Christmas and Cocos (Keeling) Islands in Australia’s Indian Ocean Territories (IOT) on two voyages over 2021 and 2022. Both voyages on the RV Investigator collected sea cucumbers using a beam trawl from the seamounts and seafloor of the area. A report of sea cucumbers collected is included below, including taxonomic treatments, shipboard and ossicle images, range extensions, and genetic data for species where available. One new species, Deima oloughlini Mackenzie and Davey sp. nov., is described. Sea cucumbers collected are now housed in the collections at the Museums Victoria Research Institute in Melbourne, Australia. Range extensions and new species records for Australia will be supplied to compliers, including the Australian Faunal Directory and Atlas of Living Australia, and genetic data will be lodged with GenBank. This report was initiated through funding by an Australian Biological Resources Study Bush Blitz grant, and subsequently supported through funding by Ocean Census. Investigating the IOT voyages were supported by Parks Australia, Bush Blitz, Museums Victoria, and other Australian institutions. Voyage time on the RV Investigator was supported by the Marine National Facility (CSIRO), and additional travel for holothuroid taxonomic work was supported by a Council of the Heads of Australian Faunal Collections grant.