No camera is waterproof unless it says so. Water-resistant models are good for, say, a Class II raft trip. A zoom lens zeros in on your subject, or pulls back for a wide-angle view. A large viewfinder is critical if you're shooting underwater. Use built-in flash even in daylight to eliminate harsh shadows.
Many flashes have a red-eye reduction feature.
Narrowing the Field With the vast array of models out there, you've got plenty to choose from. Your first decisions will concern waterproofness and film format. Consider how wet your camera is apt to get. These have rubber O-rings and gaskets to seal out drizzle or waterfall spray. Others will want a waterproof camera that can go down to about 16 feet on snorkeling trips.