Most versions of camcorders, from pocket to HD, have a waterproof version, though pocket camcorders offer the most range. Waterproof generally means that the camcorder is usable up to about 10 feet (3.05 meters) below the surface of the water. Video quality tends to suffer underwater, as does audio (if sound is even an option). But for travelers -- and beachgoers with butter fingers -- having a water-proof camcorder is a little more insurance against losing those precious vacation memories.
Clearly, a camcorder won't work well without light. Even low-light and no-light models use optics to make the technology viable. The quality of the lens is important, but more important is the optic zoom number. Most models have a standard 10X zoom -- don't go for anything less unless you'll always be shooting very close to a subject. Don't pay too much attention to digital zoom numbers, however, since this indicates only how much the electronics can artificially enlarge the image the lens captures. The more it enlarges the image, the less quality the footage will have.
Although low-light and infra-red camcorders are useful for fixed surveillance posts and ghost hunting, they don't offer much for the average consumer, and high prices don't justify the limited use.
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