Everywhere here is very casual, even the most upmarket of restaurants, the Back Porch. Leave your city gear at home and bring shorts and cotton trousers, t-shirts and sweaters, flip flops and rain gear.
Toiletries and Medical Supplies: It doesn’t rain all the time, so don’t forget to pack the sun protection – and you’ll also want to bring insect repellent as the moist atmosphere and sand dunes mean bugs of all sorts congregate here.
Listen to the weather report and bring a rain coat, and of course a bathing suit. If you wear sandals to the beach, watch out for sand briars in the dunes. They suck.
Toiletries and Medical Supplies: Bring everything you think you will need as it is expensive to buy last minute things like toothpaste and deodorant on the island.
Photo Equipment: Camera, duh.
Camping/Beach/Outdoor Gear: If you're camping bring camping gear, of course you'll want sunscreen, mosquito repellent, citronella, anti bug laser gun, etc.
Also, if you camp on the state campgrounds, there will be a public bathroom and cold cold showers so plan to bring toiletries
Clothing/Shoes/Weather Gear: If you come in the summer, bring your swim suit and some sun tan lotion. Also bring your fishing gear.