Not sure if they are, but I do know that the US Navy funded a lot of oceanographic research into predicting and understanding bioluminescence of marine organis

Not sure if they are, but I do know that the US Navy funded a lot of oceanographic research into predicting and understanding bioluminescence of marine organisms for this very reason. The surface waters of the North Atlantic have massive spring blooms of phytoplankton, which are sometimes bioluminescent, and could certainly give away the presence of a large subsurface vessel, possibly from space.