Best anchoring I"ve found is off the SW of the fort, almost directly out from the beach and the western wall. Use your charts
but there are some great sandy patches and good holding there. Held through several nights of 35+kts during our last trip while boats drug all over the inside "protected" anchorage.. You drag on the inside and it can get hairy, drag where I'm talking about and you've got miles till Loggerhead Key.
Loggerhead Key and it's surrounding dives are some of the highlights of the Tortugas. Little Africa
is an amazing dive site, the Windjammer wreck and the entire area there are beautiful. You can beach the dinghy
on the Eastern shore and walk checking out the lighthouse on the way, or bring the dinghy or even the big boat to the other side where there are mooring balls. This time of year you can probably stay as long as you want, however there is supposed to be a time limit on the balls. Don't be shocked to see huge goliath grouper hanging out under your boat, or if you are lucky enough to see the tiger shark that hangs out by the windjammer.
Some other great tips for the Tortugas..
You can get lunch everyday the ferry
is there, it's a sandwich buffet with cold drinks. You can also use the freshwater showers to rinse off. During the ferries visit the bathrooms on shore are locked, you can use the air conditioned ones on the ferry
as well during this time. Depending on the crew, you can sometimes get them to take trash for you as well. This varies.. If you find yourself needing a part or something critical, talk to the seaplane pilot, they have always been willing to (for a nominal fee) bring parts
Talk with the rangers, ask any questions, they are more then willing to guide you in the right direction. "Tree" is my favorite guy out there, if he's still there. He can answer anything you want to know.
Other then that, have fun!