If you ever wish to make this trip, we can highly recommend the crew of the Yankee Freedom. It is a 2 hour trip to the park, and the crew does their best to make it an enjoyable trip. The boat is an enclosed catamaran, and they serve breakfast on the way out. There is also a naturalist aboard who provides commentary along the way and provides an optional tour of the fort. While you can stay inside the cabin the entire trip if you wish, you are also welcome to sit topside (partially covered) or walk out to the front of the boat during the ride.
Once you reach Fort Jefferson, you are welcome to take the guided tour or to explore the fort on your own. You can also snorkel (equipment provided), or explore the perimeter. Lunch is provided on the boat, and the boat also provides the only restroom facilities as there are none for guests on the island. You arrive at the fort around 10:00 a.m., and leave for the return trip at 3:00, arriving back in Key West about 5:00 p.m. It's a very full day, but very much worth the trip.
Fort Jefferson itself is very interesting. I won't bore you with all the details here, but essentially it is one of the largest masonry forts in existence, with the bricks being shipped in from 3 different parts of the country (as is evident during the tour). It was built to protect the valuable shipping lanes there, and construction took place between 1846-1875. It remained a Union holding during the Civil War, and was used to house prisoners during that time. The fort was never 100% completed, and experienced numerous challenges during the time it was used. There was never a war-time shot fired from the fort's canons. One of the most famous prisoners to be held there was Dr. Samuel Mudd, the doctor who set the leg of John Wilkes Booth after he shot President Lincoln.
The water was a bit chilly the day we visited, but we still managed to snorkel for about 45 minutes by the fort's moat wall. The water was very clear, and while the coral was not nearly as colorful as we expected, it was still very interesting. There were also some very interesting specimens of shells, coral, and sea weeds on the shore lines, but the entire area is designated as "no take". In other words, you are not allowed to take ANYTHING from the property, including shells. Of course, that's also part of the charm of the beach area.
Just as we were leaving for the return trip, we were given the treat of seeing a very small island that is apparently the only breeding ground north of the Caribbean islands for a particular type of bird known as the Masked Booby. We saw several in flight, causing the naturalist on board to point out that it is not everyday that you are able to see flying Boobies. : ) Pictures of the birds and island are below.
This was a much anticipated trip for us. The day began very overcast and chilly, but turned out to be almost perfect weather until we had already started back. A very worthwhile day!