Make your way to Oyster Bay or Marigot, depending on the day of your tour, check in at the ferry terminal with your passport in hand.
Board the 'Voyager 3', a climate-controlled catamaran-style ferry with a bar on board. The smooth ride across the sea takes approximately a half-hour from Oyster Bay or an hour from Marigot.
When you reach Gustavia, the capital of St Barts, board a minivan to transfer to the ATV center. Once you listen to a short safety briefing and orientation to the vehicle, you're on your own. Grab a scavenger hunt map that makes hitting the island's landmarks a game or simply see where the day takes you.
After 2.5 hours, meet up in Gustavia for lunch at a local restaurant. Relax in the terrace dining room and dig in to a meal of French-influenced cuisine.
With a full belly, wander the streets of Gustavia or jump back on your ATV for 2.5 more hours of free time. Use the provided walking map of the town or head out into the unspoiled island landscape on your ATV again. Alternatively, make your way to Shell Beach to swim or snorkel (snorkeling gear provided).
At the conclusion of your 9-hour day on St Barthelemy, take the ferry back to St Maarten.