Pack lightweight, quick-dry clothing that mixes and matches easily. Bring 5-6 outfits so you don't have to do laundry. Layer strategically and check the weather and itinerary sections to be realistic about what you'll actually need.
Swim items
Swimsuit, quick-dry towel, slip-on sandals
Daypack
Small backpack to carry water, camera, and essentials while exploring
Walking shoes
One good pair of broken-in, comfortable, sturdy walking shoes is essential
Sun protection
Sun block, sunglasses, hat
Rain protection
Windproof rain jacket, poncho, or small travel umbrella
Chargers/Adapters
device chargers and electrical adapters; portable charger/power bank
Watch or Alarm Clock
Toiletries
Basic toiletries (some hotels may not provide all items); small amount of biodegradable soap for laundry
First Aid Kit
Including: lip salve, Aspirin, bandaids, anti-histamine, Dramamine, Imodium (or similar), electrolyte powder, insect repellent, extra prescription drugs you may be taking