The reason, in my opinion, for not going to the Shark anchorage if you want to do the trip in two days from Key West
is that the distance is much longer and once there, you have to sail out around Cape Romano shoals(NW about 20 miles) and then back(ENE/20 plus miles) in a large inverted V before entering Naples. The Thousand Island area option from Shark inside CRS is very shoal, continually shifting and the water
murky. The charts
are not really accurate and only an approximation of the depths. However, sailing to Marathon the first day is a nice day sail from Key West(50 miles) with unlimited anchoring
(unlike the Little Shark keyhole which is very small) and then a straight shot to CRS and then NE to Naples. And, if the weather
turns for the worse, I'd rather be sitting at Marathon than the bug hole at Little Shark. There are many ways to skin a cat. I guess I'd skin it this way. Good luck and good sailing.