The Ocean Explorer

The Ocean Explorer was a submarine used to land in the water on the planet Hydron. It was captained by Jane Clancy, but taken over later by Fleming. It was used to first collect fish roe, which Fleming had gathered from within a mountain, but then used to travel up the caves in one of the mountains to return them to the water and back to the Shoal where they belong. (NSA:  The Underwater War)