Diving Under Ice with Ctenophores
Base H - Signy Island Antarctica

Those vague long balloon shaped objects are Ctenophores - related to jellyfish, they have longitudinal lines of cilia that cause fabulous rainbow interference patterns as long as you are in the right position in relation to the light. If you're not, they just look like plastic bags as in this picture. In the winter, shoals of many hundreds or thousands would sometimes drift by. The dark patch against the ice is accumulated air while the doughnut shape is an air bubble hitting the ice.