Complex sentence: In 2016, Michelle Ridgeway explored the canyon in an eight-foot submarine in an expedition sponsored by Greenpeace, reaching a shelf at a depth of, that is a third of a mile below the surface.
Split into simpler sentences: In 2016, Michelle Ridgeway explored the canyon piloting an eight-foot submarine in an expedition sponsored by Greenpeace. She reached a shelf at a depth of, that is, a third of a mile below the surface.