Cosgrove Shoal is named after the lighthouse tender 19th century. It is
about 6 miles south of the western side of the Marquesas. This shoal goes
for miles both east and west of the light. The light itself stands in 20 feet
of water built on a dead reef. Swimming around its underwater structure
you will find lots of Barracudas standing guard over the light. This shoal is
about as close as your going to find in the Keys for being untouched. The
Gulf Stream moves in on a regular basis. When it does the visibility can be
as much as 150 feet, but normally it is around 60-80 feet.