Choose a wetsuit by matching neoprene thickness to your water temperature: 2mm suits for water in the 65-75°F range, 3/2mm for 58-68°F, 4/3mm for 52-63°F, and 5/4/3mm or thicker for water below 52°F. A wetsuit works by trapping a thin layer of water against your skin that your body warms, so the right thickness, fit, and seam sealing are what keep you comfortable on the water.
Wetsuit thickness and temperature at a glance
| Water Temp (°F) | Water Temp (°C) | Thickness | Recommended Type | Seam / Seal Type |
|---|---|---|---|---|
| >72° | >22° | N/A | Rashguard | N/A |
| 65°-75° | 18°-24° | 0.5mm - 2/1mm | Top / Shorty | N/A |
| 62°-68° | 16°-20° | 2mm - 3/2mm | Springsuit / Full Suit | Flatlock |
| 58°-63° | 14°-17° | 3/2mm - 4/3mm | Full Suit + Boots | Sealed |
| 52°-58° | 11°-14° | 4/3mm - 5/4/3mm | Full Suit + Boots + Gloves + Hood | Sealed and Taped |
| 43°-52° | 6°-11° | 5/4mm - 5/4/3mm | Full Suit + Boots + Gloves + Hood | Sealed and Taped |
| 42° and below | 6° and below | 6/5mm + | Full Suit + Boots + Gloves + Hood | Sealed and Taped |
Beyond water temperature, also weigh air temperature, wind speed, how easily you get cold, and your activity level. Colder air, more wind, low-movement activities, or a low cold tolerance all argue for a thicker suit. These are general guidelines — many brands publish their own temperature recommendations that differ slightly.
How does a wetsuit actually work?
A wetsuit is a neoprene insulation garment built for warmth and protection in watersports. It traps a thin layer of water between your body and the suit; your body heat warms that layer, slowing how fast you lose heat. Water conducts heat about 25 times faster than air, which is why a 60° day feels fine in jeans and a shirt but leaves you shivering within minutes swimming in 60° water.
A wetsuit is not meant to keep you dry. Neoprene is made of tiny closed cells filled with air that insulate against cold water by trapping heat. The thicker the neoprene, the warmer the suit, because there is more heat-trapping material. Research the water temperature where you will use the suit — accounting for seasons and swells — and if temperatures make your extremities go numb, add boots, gloves, and a hood.
What do the wetsuit thickness numbers mean?
Neoprene thickness is measured in millimeters and shown as two or three numbers separated by slashes. The first number is the thickness at the torso; the second is the extremities (or just the legs if there is a third number); the third, when present, is the arms. Thicker neoprene goes on the torso to protect your core body heat, which is vital for preventing hypothermia, while thinner neoprene on the extremities preserves flexibility. In short: the thicker the neoprene, the more warmth but the less flexibility.
How should a wetsuit fit?
A wetsuit should fit like a second skin — no sagging in the back, no excessive bunching in the arms or legs. A snug fit keeps only a thin layer of water between your body and the suit; a loose suit lets water flush through and loses effectiveness. It should also fit snugly at the neck (many sailors wear a rashguard underneath to prevent neck rash). Always consult brand-specific size charts, since fit determines both warmth and mobility.
A properly fitted suit is challenging to pull on when dry and leaves no excess room in the torso, crotch, shoulders, or knees. Once it is on, raise your arms overhead and stretch your shoulders: the motion should feel only slightly restricting. Heavy pressure means the suit is too small. You should be able to squat and move your arms easily, though suits above 5/4mm are inherently restrictive.
Which seams, zippers, and length should I choose?
Seam seals. Flatlock stitching lies flat and comfortable but lets in a little water — use it above 62°. Sealed seams (glued and blindstitched) let in very little water and suit 55° and up. Sealed and taped seams add interior taping for durability and a watertight seal — the choice for 55° and below.
Zippers. Back-zip suits run the zipper down the spine and are the easiest to get in and out of, but water can seep through the back seam and the taut back restricts bending. Chest-zip suits are trickier to enter but keep water out far better, offer a comfortable low-rash neck, and flex more in the back. Zipperless designs on lighter suits (3/2mm and thinner) and neoprene tops prioritize mobility over warmth.
Lengths. Full suits cover the whole body to wrists and ankles and come in many thicknesses. Shorty / springsuit / short john styles use thinner material with short arms and legs for warm water. Long John/Jane suits are full-length but thin (usually 1.5-2mm) and sleeveless. Wetsuit tops (0.5-2mm) pair with boardshorts or layer under a full suit for extra core warmth, and rashguards are light Lycra shirts for sun protection or as an under-layer.
What about FAR infrared and cold-water accessories?
Some wetsuits use FAR infrared technology, with mineral-enriched fibers that capture body heat and convert it to far infrared rays. NASA found that rays between 6-14 microns can penetrate the body, raising temperature, improving circulation, and stimulating cell growth. Because these suits generate heat rather than only reducing heat loss, they let you wear a thinner, more flexible suit in colder water.
In water colder than 60°, add accessories. Neoprene gloves range from five-finger (most dexterity) to mittens (warmest for icy water), with three-finger hybrids in between. Boots come in round-toe or split-toe designs for agility, and hoods can be added to hoodless suits — some suits build the hood in.
Frequently asked questions
What thickness wetsuit do I need for cold water?
For water between 52° and 58°F, use a 4/3mm to 5/4/3mm full suit with boots, gloves, and a hood; below 42°F step up to 6/5mm or thicker with sealed-and-taped seams.
How should a wetsuit fit?
It should fit like a second skin with no sagging or bunching — snug enough to trap only a thin layer of water. A correctly sized suit is hard to pull on when dry and only slightly restricts overhead arm movement.
Does a wetsuit keep you dry?
No. A wetsuit traps a thin layer of water against your skin that your body warms; the neoprene's closed air cells then insulate you. Staying dry is the job of a drysuit, not a wetsuit.
What is the difference between flatlock and sealed seams?
Flatlock seams lie flat and are comfortable but let in a little water, best above 62°. Sealed (glued and blindstitched) or sealed-and-taped seams block nearly all water for colder conditions.
Back zip or chest zip — which is better?
Back-zip suits are easiest to get in and out of but can let water in at the back seam. Chest-zip suits are harder to enter but keep water out better and flex more, making them warmer overall.
When do I need boots, gloves, and a hood?
Add neoprene accessories once water drops below about 60°F, especially if your extremities go numb. They dramatically extend how long you can comfortably stay in cold water.