What wetsuit thickness for which water temperature

The short answer

As a broad rule, PADI describes 3 mm suits as warm-water suits, 5 mm as temperate-water suits and 7 mm as cold-water suits. A scuba chart published by Divernet, produced in partnership with a dive retailer, gives these bands for water temperature:^4,5

• Over 28°C: a swimsuit, rash guard or dive skin⁵
• 25–27°C: a 2 mm shorty or a 1 mm full suit⁵
• 22–24°C: a 3 mm full suit⁵
• 17–21°C: a 5 mm full suit⁵
• 10–16°C: a 7 mm full suit or an 8/7 mm semi-drysuit⁵
• 5–10°C: an 8/7 mm semi-drysuit or a drysuit⁵
• Under 5°C: a drysuit⁵

Why charts disagree

Charts are a starting point, not a rule. A chart from Scuba Diving magazine gives two columns for each temperature band, one for divers who run warm and one for divers prone to cold; at 73–79°F (about 23–26°C) it suggests anything from a 2 mm shorty to a 3 mm full suit for the first group and a 3 mm to 5 mm full suit for the second.⁶

The same magazine notes that everybody has a different internal thermometer, and that the number of dives, their depth and their length also affect the choice. A PADI article likewise says wetsuits can keep divers warm between 10°C and 32°C, but that this varies from diver to diver.^3,6

Hoods, gloves and boots

Scuba Diving suggests experimenting with hoods, vests and gloves to find your personal comfort zone. PADI notes that an attached hood stops cold water flowing in through the collar, and that hooded vests can be worn under a wetsuit. A PADI blog author reports wearing their wetsuit comfortably in 8°C water with a good hood and gloves.^3,4,6,7

Hands deserve attention in cold water. DAN's Alert Diver magazine explains that their small mass relative to surface area means they lose heat quickly.⁸

When to switch to a drysuit

Sources set the drysuit threshold at different points. The Divernet chart offers a drysuit as an option from 10°C down and as the only choice below 5°C, while the Scuba Diving chart already suggests a drysuit in the 50–65°F band (about 10–18°C) for divers prone to cold. DAN's Alert Diver says that as temperatures become more extreme, a drysuit is the only practical protection.^5,6,8

Scuba Diving also suggests considering a drysuit if a lot of your diving is deep, whether the water is cold or not. DAN Europe stresses having the right protective equipment and experience before diving in cool or cold water.^1,9

Warm water: rash guards and dive skins

In very warm water, a rash guard and shorts may be all you need. Rash guards help protect skin from the sun and from stinging life such as fire coral and jellyfish, and can be worn under a wetsuit to stop seams rubbing. Dive skins have little or no insulation and are intended for very warm water or as an extra layer under another exposure suit.^7,10

Warm does not mean no protection at all. A DAN Europe article on hypothermia says most divers benefit from thermal protection in water cooler than 27°C.¹

Why you get colder with depth and over a trip

Neoprene insulates through tiny gas bubbles, and those bubbles compress with depth. Scuba Diving explains that at 33 feet (10 m) the pressure has doubled, taking nearly half the insulation from a wetsuit, and that by 99 feet (30 m) the suit has practically no insulation left. DAN's Alert Diver makes the same point for neoprene drysuits.^8,9

Scuba Diving notes that the biggest heat loss out of the water is likely to be during the surface interval, and that gradual heat loss goes unnoticed but adds up over several days of diving. Its advice is to undress and towel off between dives; DAN also notes that wet skin cools through evaporation and advises drying the skin and replacing damp layers.^2,9

Cold can lead to hypothermia even in warm water through slow body cooling. If you have questions about cold exposure and your own health, ask a dive physician or contact DAN.¹

Before you go

• Check the expected water temperature for your dates and compare it with more than one chart.^5,6
• If you feel the cold easily, use the cold-prone suggestions or add a hood, vest or gloves.⁶
• Consider a hood or hooded vest: an attached hood stops cold water entering through the collar, and a hooded vest can be worn under a wetsuit.^4,7
• For very warm water, bring a rash guard for sun and sting protection, or a dive skin.^7,10
• On multi-dive days, undress and towel off during surface intervals.^2,9