Set in 1905, Thalassa is a first-person psychological drama following Cam, a deep sea diver aboard an expedition to raise a long-forgotten Spanish galleon. What begins as a historic triumph takes a devastating turn — and when Cam resurfaces after recovering from the incident, the crew is gone and the ship rests broken on the ocean floor. Guided only by support diver Bailey from above, Cam descends once more to find the truth about what happened in those final moments.