To lend understanding to the metaphor, "the tip of the iceburg"
EVER SEE AN ICEBERG FROM TOP TO BOTTOM?
This is an awesome composite photograph! It 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!  In this particular case the water was calm, & the sun was almost directly overhead so that the diver was able to get into the water and click this pic. Clear water huh?!
They estimated the weight at 300,000,000 tons. And now we know why they say one picture is worth 1000 words....and now we also know why the Titanic sank!