Land at Gustaf III Airport (SBH), step onto a private boat, and be on Saint-Martin in about 37 min. No ferry timetable, no overnight on the wrong island — the transfer is timed on your flight.
The public ferry runs on its own timetable and rarely matches an arriving flight; a missed connection means a night on Saint-Barthélemy instead of Saint-Martin.
A private transfer leaves when you land, takes your luggage in one go, and covers the 29 km in about 37 min.