You don't need to bring an beach umbrella with you during a swell, but absolutely bring a chair. In August, Hurricane Bill passed Long Island on its way to Canada, and we decided to go see how a 15 foot swell would affect our go to spot. There was no beach - the water was coming all the way to the dunes. The sheer power of the ocean was mind blowing - both intimidating and beautiful all at once.
This beach is great if you want to get away from the city. Everyday here is like a vacation. It cost a few bucks to park in the lot, but its worth every penny when you pile eight of your closest friends in the car and make a full day out of the sunshine and sand.
If you're on St. John at all you're going to pretty stoked no matter what you do or where you go. With about seventy percent of the island devoted to a National Park St John is a beautiful place. The Island's edge is littered with bays, coves and beaches. I spent some quality time at Hawksnest Bay.