Packing

Travel light, and make sure you can carry your luggage without assistance. Even if you're planning to stay only in luxury resorts, odds are that at least once you'll have to haul your stuff a distance from bus stops, the shuttle drop-off, or the airport. Another incentive to pack light: domestic airlines have tight weight restrictions (at this writing 11.3 to 13 kilograms [25 to 30 pounds], and sometimes less for their discounted fares) and not all buses have luggage compartments. Frameless backpacks and duffel bags can be squeezed into tight spaces and are less conspicuous than fancier luggage.

Bring comfortable, hand-washable clothing. T-shirts and shorts are acceptable near the beach and in tourist areas; long-sleeve shirts and pants protect your skin from ferocious sun and, in some regions, mosquitoes. Leave your jeans behind—they take forever to dry. Pack a waterproof, lightweight jacket and a light sweater for cool nights, early mornings, and trips up volcanoes; you'll need even warmer clothes for trips to Chirripó National Park or Cerro de la Muerte and overnight stays in San Gerardo de Dota or on the slopes of Poás Volcano. Bring at least one good (and wrinkle-free) outfit for going out at night.

Women might have a tough time finding tampons, so bring your own. For almost all toiletries, including contact lens supplies, a pharmacy is your best bet. Don't forget sunblock, and expect to sweat it off and reapply regularly in the high humidity. Definitely bring sufficient batteries, because they're expensive here.

Snorkelers staying at budget hotels should consider bringing their own equipment; otherwise, you can rent gear at most beach resorts.

You have to get down and dirty—well, more like wet and muddy—to see many of the country's natural wonders. This following packing list is not comprehensive; it's a guide to some of the things you might not think to bring. For your main piece of luggage, a sturdy internal-frame backpack is great, but a duffel bag works, too. You can get by with a rolling suitcase, but then bring a smaller backpack as well.

Packing List for Costa Rica

Quick-drying synthetic-fiber shirts and socks

Hiking boots or shoes that can get muddy and wet

Waterproof sport sandals (especially in the Osa Peninsula, where most transportation is by boat, and often there are no docks)

Knee-high socks for the rubber boots that are supplied at many lodges

A pair of lightweight pants (fire ants, mosquitoes, and other pests make covering yourself a necessity on deep-forest hikes)

Pants for horseback riding (if that's on your itinerary)

Waterproof, lightweight jacket, windbreaker, or poncho

Day pack for hikes

Sweater for cool nights and early mornings

Swimsuit

Insect repellent (with DEET, for forested areas and especially on the northern Caribbean coast, where there are pockets of malaria)

Flashlight or headlamp with spare batteries (for occasional power outages or inadequately lighted walkways at lodges)

Sunscreen with a minimum of SPF 30 (waterproof sunscreens are best; even if you're not swimming, you might be swimming in perspiration)

Large, portable water bottle

Hat and/or bandannas (not only do they provide shade, but they prevent perspiration from dripping down your face)

Binoculars (with carrying strap)

Camera (waterproof, or with a waterproof case or dry bag, sold in outdoor-equipment stores)

Film (film in Costa Rica can be expired and is expensive)

Imodium and Pepto-Bismol (tablet form is best)

Swiss Army knife (and remember to pack it in your checked luggage, never your carry-on—even on domestic flights in Costa Rica)

Zip-style plastic bags (they always come in handy)

Travel alarm clock or watch with an alarm (don't count on wake-up calls)

Nonelectric shaving utensils

Toilet paper (rarely provided in public bathrooms)