This image dataset provides ultrastructural micrographs of Antarctic deep-water sponges (Demospongiae and Hexactinellida) collected for study of microbial symbionts and histology during expedition JR17003a (RRS James Clark Ross, 2018) in Prince Gustav Channel, western Weddell Sea. Formalin-fixed sponge tissues were rinsed twice in PBS and postfixed in 1% osmium tetroxide in phosphate buffer for 6 hours at 4°C. Tissues were then rinsed twice in distilled water, dehydrated through to 100% ethanol and embedded in epoxy (TAAB 812). Ultrastructural sections of 60 nm were cut with a Leica Ultracut T microtome, stained in uranyl acetate and lead citrate, and then viewed and photographed with a Philips Morgagni transmission electron microscope equipped with a Gatan CCD camera. Image files are labeled with expedition, station and sample ID. Each image includes a scale.