Re: St Maarten itinerary - 9 days
Saba was my first thought too.. And it's possible to be picked up at the bay near the moorings (Wells Bay IIRC).. It's a bit of a trick landing a dinghy there though. The drive up out of Wells is worth it!
You'll not find a more unique place in the region. If your group is fit climb the 1000 steps at Windwardside to the tropical jungle at the peak.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"