Good Morning! There is a Grand Marche at the roundabout at Bush Road. They have deli counter in the back as well as a large selection of meats, groceries and just about anything else you might need--very large store. You should find this on your way to Philipsburg. As for snorkel equipment, Aqua Marina operates the water-sport activities at Divi Little Bay and I think the Simpson Bay Resort and they have goggles and masks. Divi Little Bay is near Philipsburg if you can make a quick stop, that might work for you.

Hope you are enjoying your vacation!