Wear anything comfortable and light. Temperatures could be average 29-36 degrees celcius here all the time. Flipflops is the best foot wear.
Toiletries and Medical Supplies: A water resistant insect repellent is a good essential supply to bring. There were 8 us, but i got the most bites, in my face, in my back ( a lot!!) in my arms and legs...i must have been the sweetest one among us! You won't feel them biting, until a day or two, when all these redness and bumps appears! And boy, it does itch!
Photo Equipment: Water -proof camera or digicam would be perfect, as most of your activities are water based. Or if your gear are not water proof like mine, good all plastic bags are okay.
Camping/Beach/Outdoor Gear: Bring a tent, just in case it rains. Otherwise, sleeping under the stars in your sleeping bag is a good, if not better. Try the local sleeping mat called " Banig" and the local blanket "Malong"