Wetsuits, Semi-Drys and Drysuits: Which Thickness for Which Water Temperature?

An exposure suit keeps you warm and protects your skin from sun, scrapes and stinging creatures. Staying warm isn't just about comfort. Cold divers use more air, tire faster, and may be at higher risk of decompression sickness. Choosing the right suit for the water temperature is one of the most useful things you can learn.

How each type of suit works

Wetsuit

Made of neoprene, a rubber foam full of tiny gas bubbles that insulate you. A thin layer of water enters the suit and is warmed by your body. A snug fit is crucial: if water keeps flushing in and out, you lose that warmth.

Semi-dry suit

A thick wetsuit (usually 6–7 mm) with sealed seams, tight wrist/ankle/neck seals and a waterproof zip that limit water flow. You still get a bit wet, but much less water circulates. Great for 12–20 °C water.

Drysuit

A waterproof suit with latex or silicone seals at the neck and wrists (or dry gloves) and attached boots. You stay dry, and warmth comes from insulating undergarments worn underneath. Drysuits have inflation and exhaust valves because the air inside compresses with depth. They need a specialty course, because buoyancy control is different.

Wetsuit thickness by water temperature

Everyone feels cold differently, but this table is a solid starting point. Use our wetsuit thickness calculator for a personalised answer.

Water temperature	Suggested protection
29 °C+ (84 °F+)	Rash guard, dive skin or 1–3 mm shorty
26–29 °C (79–84 °F)	3 mm full suit (or shorty if you run warm)
22–26 °C (72–79 °F)	5 mm full suit, or 3 mm plus a hooded vest
18–22 °C (64–72 °F)	7 mm full suit, hood, boots; gloves if allowed
12–18 °C (54–64 °F)	7 mm semi-dry with hood and gloves, or a drysuit
Below 12 °C (54 °F)	Drysuit with suitable undergarments

Shorty vs full-length suit

• Shorty (short arms and legs): cool, easy to put on, great for very warm water and snorkeling.
• Full suit: warmer and protects arms and legs from sun, scrapes, jellyfish and fire coral. Most divers wear full suits even in the tropics.
• Two-piece / layering: a hooded vest over or under a suit adds a lot of warmth, especially around the core and head.

Hoods, gloves and boots

You lose a lot of heat from your head. A hood or beanie makes a big difference in water below about 24 °C. Boots are needed for open-heel fins. Note that gloves are banned in some marine parks (for example parts of the Red Sea and the Caribbean) to stop divers touching the reef. They're for cold water and wrecks, not tropical reefs.

How a wetsuit should fit

• Snug everywhere, like a second skin, with no baggy areas in the lower back, armpits or knees
• You can breathe deeply and raise your arms fully
• The neck seal is close but doesn't choke you
• Arms and legs reach your wrists and ankles

Wetsuits compress at depth and lose some warmth. Tip for getting them on: wear thin socks or put a plastic bag over your foot or hand, and roll the suit up rather than pulling.

Buoyancy and weighting

Neoprene floats, and thicker suits need more weight. A 7 mm suit may need twice the lead of a 3 mm suit. Whenever you change suits, do a buoyancy check. Remember that neoprene compresses as you descend, so you become heavier at depth.

Buy or rent?

Rent at first, since the right thickness depends on where you dive. Buy when you dive regularly in one kind of water, or if rental suits don't fit you well. A good 3 mm or 5 mm suit costs about US$150–400; a semi-dry US$300–600; a drysuit US$800–3,000+ plus undergarments.

Care

• Rinse inside and out in fresh water after every dive day. Wetsuit shampoo helps with smells.
• Dry it inside out, in the shade. UV breaks down neoprene.
• Hang it on a wide hanger, not a thin wire one, and never fold it tightly.
• Lubricate zips with wax or zip lubricant, especially on drysuits.

Frequently asked questions

What thickness wetsuit do I need for 25 °C water?

A 5 mm full suit, or a 3 mm suit with a hooded vest, is comfortable for most people at 25 °C, especially if you're doing several dives a day.

Can I use a surfing wetsuit for scuba diving?

Surf wetsuits are designed for flexibility at the surface and are often thinner in places. They work for shallow warm dives, but scuba-specific suits keep you warmer at depth.

Is a drysuit hard to use?

It takes a specialty course and some practice, because you manage air in the suit as well as your BCD. After a few dives, most people find it very comfortable in cold water.