Neoprene chest waders are intended for use in water that is approximately waist deep, in slow-moving or still waters. Leaving the extra clearance between the water level and the top of your waders gives you a margin of safety in case of stepping into hidden holes, sudden waves, boat wakes or swift current. Because neoprene isn't breathable, it's a poor choice for areas where a lot of continuous movement will be necessary.
Neoprene chest waders may come in one of two designs: stockingfoot or bootfoot. Stockingfoot waders cover the entirety of your legs and feet, just as a baby's footie pajamas do. They'll keep you dry and warm, but you must wear shoes over the wader's stocking feet to protect against punctures. Bootfoot waders have waterproof boots, usually made of rubber, attached directly to the lower portion of the wader leg. This eliminates the need to wear extra footwear but makes the waders heavier and may restrict leg movement.
In case of an accidental dunking, chest waders may flood with water and weight you down, putting you in danger of drowning. Wearing a wading belt---which cinches around your torso to keep water from flooding in in case of accidental immersion---may save your life.
Always rinse your neoprene waders off after use, especially if they've been used in saltwater. Hang them upside down to air dry. Once they're dry, crumple newspaper and stuff it into the feet and legs of the wader to help hold its shape, then hang the waders upside down in a cool, dark place. Above all you want to avoid creasing or folding the waders, as over time these fold lines may crack or leak.
Neoprene waders can cost anywhere from $80 to $400 or more, depending on neoprene thickness, size and whether they're bootfoot or stockingfoot.
Always try on waders before purchasing them. Neoprene waders may fit more snugly than other types of waders because the neoprene stretches, but try to leave as much extra room as you can without hindering your own movement. The extra space will make getting in and out of the waders easier, plus give you the chance to layer extra clothing under the waders, if necessary, to help you keep warm.