This is a rainforest environment and as such it is very difficult for your clothes to dry within 24 hours. So bring zip locks for the wet items.
Small backpack for bus and day trips
Water bottle
Raincoat or rain poncho
FLASHLIGHT
Sunglasses
Sunscreen
Insect repellent ( the only time you will have a need for this is on the Liquid Lava hike)
Camera (optional; store in Ziplock or other waterproof bag)
Binoculars (optional; store in Ziplock or other waterproof bag)
Personal toiletries
Comfortable footwear
Water sandals
Swimwear
Light weight long pants
Casual wear for night (optional)