I just spent a week at the beautiful Marquis Boutique Hotel in St. Marten! The hotel is spacious and clean and the staff wonderfully helpful. The rooms have stunning balconies overlooking the marina. There is a small pool to cool off in, a bar for sampling the owners wine, and a covered porch where fruits, pastries, coffee and tea is served every morning. This isn't immediate beach access as the hotel is up a steep hill, but Anse Marcel is a very short drive (by the hotel shuttle or a rental car) down the hill. The beach is free and shared with two other hotels. The water is extremely calm at Anse Marcel and there are water sports available to you, two beach bars with drinks and snacks, and free pool access at the Le Domaine Hotel (where you access the beach).
The island of St. Marten is rather small and even though the Marquis is located north, you can be nearly anywhere in a very short time. A rental car is most helpful but be careful of traffic during high season. Grand Case is very close to the hotel and has a restaurant to please any palate. Marigot is 15 mins away and Phillipsburg is 20-25 mins. away. There are plenty of beaches to discover in both sections of the island and if you're ever lost, people are so willing to smile and help you on your way.