Simpson Bay was the home of a Danish fishing community and for many years there was no bridge over the marshy area that allowed flow in and out of the lagoon. Things change. Today a large drawbridge opens six times a day to let mega-yachts into the Isla del Sol Marina and Princess Juliana Airport is next door. In 2012/3 a causeway was built from the airport to the Dutch side of the border on the eastern side of the lagoon. The area is ringed with hotels, casinos, and restaurants. There so many restaurants that we have split the area into two sections. Simpson Bay West is the area on the western side of the Dutch Bridge, closest to the Airport and Simpson Bay East is the area on the eastern side of the Dutch Bridge running through Cole Bay to the French border.
Simpson Bay Beach is about two miles long and, for the most part, has little development. There are private homes and small hotels and guesthouses on the western part. The eastern part, also called Kimsha Beach, has several large hotel and timeshare complexes with considerable watersports activities. The calm bay and the dockage in the lagoon also attract charter boats.
There is shopping, notably at the Maho Resort, but also in other resorts and in several standalone facilities. As real people live in this area, one finds gas stations, supermarkets, doctors, etc. in addition to the usual tourist shops.
If you are staying in this area, you'll find most everything you need, and probably within walking distance.
Here's several webcams from the Simpson Bay Resort showing their end of Simpson Bay.