Drysuits are used in cold to very cold (even polar) conditions. They are constructed from a waterproof material and have latex rubbers seals around the wrists, neck and ankles. Some have an integrated sealed booties for the feet.
Drysuits have the following advantages over wetsuits:
Loose fit, more like normal clothing
Staying dry inside can Increase comfort
Warmth can be adjusted by wearing different undergarments
Substantially better protection against cold water
A general rule of thumb is if you are shivering in your wetsuit, consider using a drysuit.
Ocean Rodeo Soul drysuit review