Most cruise ships drop anchor off the Dutch capital of Philipsburg or dock in the marina at the southern tip of the Philipsburg harbor; a very few small or medium-size ships drop anchor in Marigot Bay and tender passengers ashore in the French capital. If your ship anchors, tenders will ferry you to the town pier in the middle of town, where taxis await passengers. If your ship docks at the marina, downtown is a 15-minute taxi ride away. The walk is not recommended. The island is small, and most spots aren't more than a 30-minute drive from Marigot or Philipsburg.
Doing your own thing will be much less expensive here than a ship-sponsored tour, and since rental cars are cheap (starting at $30 per day for a local car rental), you can easily strike out as soon as your ship docks. This is the best thing to do if you just want to see the island and spend a little time at a beach. Compare costs of ship excursions and activities to prices offered directly by the operators on their websites to make sure you're saving the most money. Taxis are government-regulated and fairly costly, so they aren't really an option if you want to do much exploring, but if you just want to go to a beach for the day, there are taxis at the dock. Authorized taxis display stickers of the St. Maarten Taxi Association. Taxis are also available at Marigot. You may be able to negotiate a favorable deal with a taxi driver for a two- to three-hour island tour for as little as $70 for two passengers or $30 per person for more than two.