These Ain't Your Daddy's Tightey-Whities A drysuit is only half of the warmth equation for cold-water diving. The shell keeps you dry, but it's the fluffy fleece underwear that beats back the cold and helps you retain body heat and stay comfortable during the dive. Most manufacturers have jumpsuit-style underwear specific to their suits and specific to the cold factor of the area you'll be diving. Instead of the off-the-shelf fleece you'll want to get the manufacturer-designed suits, because they're made to give you maximum warmth and unrestricted motion as well as to wick moisture away from your body. Plus, they're cozy and comfortable enough to wear in front of the fire after the dive while sipping on hot chocolate. All our drysuit manufacturers have their own undergarments.

White's Glacier MK Series Wear it under your drysuit or wear it after the dive -- either way it'll keep the chill at bay in style. The Glacier MK Series is made up of four garments that can be layered to meet the dive conditions. The MK1 John and MK1 Long Sleeve T are made from MK1 MicroFleece, which provides just enough insulation for warmer dives. Add the MK2 Base John and/or MK2 Base Jacket and you'll have all the insulation you'll need. Zippered sleeves can be taken off the jacket and put on the john to create a one-piece suit. Both pieces have StormProof 70-denier micro-ripstop water-resistant Taslon nylon facing, and the john incorporates 1 mm Lycra/neoprene stretch expansion panels at the waist and knees for excellent mobility. Bi-directional zippers and strategically placed convenience panels take the stress out of answering nature's call. The MK2 Base Jacket also features a detachable hood, fleece-lined hand-warming pockets and a face guard, which make it functional for any topside excursion. MSRP: MK1 John or Long Sleeve T, $58; MK 2 Base John or Base Jacket, $149.95 Contact www.whitesdiving.com

BARE CT200 Polarwear Extreme Built for all-around cold-water diving, this garment gets its insulating power from B200 Thinsulate married to a 7.5 ounce brushed polyester fleece. The outer shell is a low-friction fabric that makes sliding into your drysuit easier than ever. Hydrostretch panels at the elbows and knees boost flexibility, as does a special LUMBARE-X-TENDER panel at the lower back. An extra-long two-way front zipper makes donning and doffing a breeze. The women's model also has a specially designed convenience zipper. Foot stirrups and thumb loops help keep the undergarment in place, and a ribbed knit collar and cuffs provide a secure fit. MSRP $289.95 Contact www.bare-wetsuits.com

DUI Thinsulate Insulation 200 gram & Thinsulate Ultra Insulation 400 gram This one-piece jumpsuit is available in two weights and uses premium Thinsulate insulation -- the same already-compressed material used to insulate quality footwear is perfect for the rigors of diving. The jumpsuit features a two-way zipper, soft fleece lining and hand-warmer pockets. An outer microfiber shell protects the wearer from wind and spray while on the dive deck. The 200-gram suit is best for use in 55- to 65-degree water, while the 400-gram suit is designed for 35- to 50-degree conditions. The 400-gram suit is also quilted. Available in production and custom sizes. MSRP: (production suits) 200-gram, $358; 400-gram, $418 Contact: www.dui-online.com

Dive Rite EX922 To complement their EX905 expedition-quality drysuit, Dive Rite offers a 5-ounce Primaloft jumpsuit that provides great insulation in cold-water conditions. Divers in more moderate temperatures (such as Florida cave divers) can don Dive Rite's 4-ounce Primaloft Shortie to keep the core warm. Primaloft stands up well to compression and retains 80 percent of its insulating ability when fully soaked. These suits incorporate a Hydrofil inner layer designed to be worn against the skin to wick moisture. The garment's outer layer is denier to repel moisture, provide durability and reduce friction when donning the drysuit. To battle heat loss in the most susceptible areas, Dive Rite also offers two other garments, a PolarTec Classic 200 Vest and a Neck Warmer. Both are breathable, dry quickly and can be used with various undergarments. MSRP: 5-ounce Jumpsuit, $319; 4-ounce Shortie, $199; Neck Warmer, $26; Vest, $69. Contact www.diverite.com

Pinnacle Aquatics Pinnacle's Evolution undergarment boasts 200 grams of total insulating weight. Half of this comes as a layer of Thinsulate, the other half as warm technical fleece. Together they provide adequate insulation for diving waters from 37 to 55 degrees. The outer shell is made of ripstop nylon for durability, and the suit features two fleece-lined hip pockets, one zippered chest pocket and a long two-way entry zipper. Unique to the Evolution are special neoprene wrist and ankle cuffs, which not only help insulate but also are specially designed to prevent material from bunching up in these critical areas. For somewhat warmer waters, divers may choose Pinnacle's Temperate undergarment, designed for 47- to 65-degree water. Made from technical fleece, it has two hip pockets for storing small stuff and thumb loops and ankle stirrups for easy drysuit donning. Both suits feature two-way zippers. MSRP: Evolution, $229; Temperate, $169 Contact www.pinnacleaquatics.com