Hiking Boots (Maya Coast is often wet and the tropical evergreen forest is branchy and thick)
Socks (wool or capilene blende, something that wicks away sweat), lite weight, 3 pairs
Liner socks, 3pairs (depends on if you use liners, we each have our own system!)
Tivas or similar sandels (something that securely stays on your foot when you're wading)

Underwear, 4 pair, preferably something like Patagonia silk weight capiline(for town and field); you can get by with cotton/nylon.

Pants, 2-3 pair, micro-fiber, such as SUPPLEX(e.g. Royal Robbins, Gramicci). These are amazing, lite weight, super cool, incredibly comforable, wash easily and dry very fast. You could get by with other lite weight fabrics.
Shorts
Pants (optional), cotton (for town); skirt (for town) (nice to wear a long skirt in the Mayan villages or whenever you get the chance.) Also, nice to save a set of clean clothes for when you get on the plane to return home.

Bathing suit (consider the extremely strong sun; for snorkeling consider you will be exposed for hours...protect your self from radiation and skin cancer)

Supplex, micro-fiber long sleeve shirts, 3 (you can always roll up the sleeves, good for sun protection and nasty insects); These are amazing, lite weight, super cool, incredibly comforable, wash easily and dry very fast. You could get by with other lite weight fabrics.
Cotton t-shirt, 2 (good for sleeping and those days you just can't resist)

Rain Shell like a poncho, it's hot and humid in the tropics, a tight mountain GORTEX shell is overkill.

Umbrella (short, lite weight, good in the tropical Maya Coast for those afternoon thunder showers)

Baseball cap or other sun shade hat

Backpack, (use this as your luggage case, it'll make moving around a lot easier; highly recommend the Mountainsmith Mountain-Lite Backpacks)
Day pack (good sized one for hauling field gear for our field work)

Sleeping Bag: Summer, super light weight

Sleeping Pad: e.g. mountain hardware or thermarest. In the first couple of days you can also buy a few cheap blankets and use that for your pad.

Flashlights, bring extra batteries. Bring 2; one powerful one for night hikes and one that is good for reading at night in your room or tent, the new 3-4 LED headlamps by Black Diamond and Petzl are excellent.

Swiss Army Knife or Leatherman Tool
2 1-litre water bottles (consider hydration systems like Platypus or Camelback or MSR)
Binoculars (a must for wildlife viewing)

Camera: you'll truly regret it if you don't bring a camera. But also remember that sun, surf and sand aren't the best friends of photo gear. If you're digital and battery intensive then please bring lots of extra batteries and memory. You won't have much chance to recharge.

Snorkel, Mask and Flippers: Yes, you must bring these from home. Please check them out in your local pool and get used to breathing through a snorkel, looking through a mask, and moving around and staying afloat with flippers BEFORE you arrive. You'll enjoy your self so much more and get more out of the course if you arrive comfortable with snorkeling. Our master diver, David Wojnowski, will review snorkel skills and safety on our first visit to the reef.

Personal First Aid Kit
Personal medications
Personal toiletries
Personal shower & bathing towel

Sunglasses with retainers
Sunscreen
Lip block

Bug Repellant

Pen, pencils

personal journal

Field notebook: a place to record your educational, scientific and natural history field notes. Something that fits into your pocket or daypack and that you will have with you at all times. The learning opportunities are so rich and it's best to record these as they occur rather than depend on your memory.

Favorite dry snacks

A hidden wallet: many models sold by Eagle Creek are excellent. They hang on your neck or wrap around your waist and remain under your shirt, skirt or pants. Very secure for keeping your passport and money handy and safe.

Wristwatch: Plastic cheap Casio. This is required because the entire team is dependent on everyone knowing what time it is. For some it's tempting to take off your watch. Please save that experience for after the course.

We recommend that you do not wear valuable jewelry. Don't invite trouble.