A polarizing filter will reduce glare from reflections, darken blue skies, and increase color saturation. Outfitters usually provide metal ammo boxes to keep your equipment dry and safe. Discuss your needs when you make your reservation. On overnight trips, see if there's enough space for you to have two ammo boxes one to store your extra equipment, the other to keep close at hand with film, lenses, batteries, and a lens-cleaning kit. To prevent a meltdown of camera and film, put your gear in an ammo box that's painted white or cover it with a spare shirt or towel.
Dark boxes heat like ovens when exposed to the sun.
In addition to ammo boxes, airtight plastic bags are ideal for sealing out moisture and grit. For maximum protection and convenience, pack your camera in a plastic, foam-lined case, available at camera stores. Water, sun, and impacts are threats to camera gear, but more dangerous are sand and grit, which can easily scratch a lens. Be sure to protect your equipment at the campsite. Waterproof disposable cameras are a great low-cost alternative.