Besides your usual packing you could also consider:
Flashlight or headlamp and an extra battery
1 pair lightweight long pants
Sun protection clothing such as long sleeved rash guards
Sun hat and sunglasses
Any necessary medications or vitamins
Your swim suit or swim shorts, (of course)
NOTE: keep in mind that this is a very remote location, so if you have particular needs that are even slightly uncommon it’s best to bring it with you as supplies can sometimes be difficult get.