This is awesome! This apparently came from a Rig Manager for Global Marine Drilling in St. Johns, Newfoundland. They actually have to divert the path of these things away from the rig by towing them with ships!
Anyway, in this particular case the water was calm and the sun was almost directly overhead so that the diver was able to get into the water and click this pic. Clear water huh?! I guess you CAN only 'see' the top 10%ish! They estimated the weight at 300,000,000 tons!