It is as ominous as it sound. There is a stretch of the ICW known as the Rock Pile, which was carved out of a stone bottom, and which is so narrow that you cannot pass another boat and must make what is known as a securitae call to alert oncoming vessels that you are proceeding through. Add to that the occasional, large commercial vessel and it makes for an interesting transit. Here are some photos at low tide.
M/V Leap of Faith 