Possible Clues:

• Big enough to start with to have six feet
• Unit of depth - comprehend it
• Can you penetrate such a deep mystery?
• Measure of depth, 6 ft.
• Six feet wide to start with
• Six feet; make sense of
• A couple short of 3 down down in the sea
• A measure of six feet in depth
• Get to the bottom of sound
• It equals six feet