Pack light. Baggage carts are scarce at Central American airports, and international luggage limits are increasingly tight. Tropic Air and Maya Island Air officially have 70-pound (32-kilogram) weight limits for checked baggage. However, in practice the airlines in Belize rarely weigh luggage, and if you're a little over it's usually no problem. Occasionally, if the flight on the small Cessna or other airplane is full and there's a lot of luggage, some bags may be sent on the next flight, usually no more than an hour or two later.
Bring casual, comfortable, hand-washable clothing. T-shirts and shorts are acceptable near the beach and in tourist areas. More modest attire is appropriate in smaller towns, and the same long sleeves and pants will protect your skin from the ferocious sun and mosquitoes. Bring a hat to block the sun from your face and neck. If you’re on a boat, you’ll want a tight-fitting cap or hat with chinstrap to keep it from being blown away.
If you're heading into the mountains or highlands, especially during the winter months, bring a light sweater, a jacket, and something warm to sleep in, as nights and early mornings can be chilly. Sturdy sneakers or hiking shoes or lightweight boots with rubber soles for wet or rocky surfaces are essential. A pair of sandals (preferably ones that can be worn in the water) are good, too.
Be sure to bring insect repellent, sunscreen, sunglasses, and an umbrella. Other handy items include tissues, a plastic water bottle, and a flashlight (for occasional power outages or use in areas without streetlights). A mosquito net for those roughing it is essential, but people staying in hotels or lodges—even budget-level ones—rarely need one. Snorkelers should consider bringing their own equipment, especially mask and snorkel, if there's room in the suitcase. Divers will save money—typically BZ$50 a day in rentals—by bringing their own equipment. Sand and high humidity are enemies of your camera equipment. To protect it, consider packing your gear in plastic ziplock bags. Also bring your own condoms and tampons. You won't find either easily or in familiar brands.