What you wear under your wetsuit changes how long you can stay in the water, how comfortable you are while you're there, and how much you dread getting changed afterwards. 

This guide covers the full layering system for cold water and the simpler approach for summer:

Suitable for: surfers, open water swimmers, divers, and anyone who has ever cut a session short because they got too cold.

Cold water layering follows a simple principle: cover the areas that lose heat fastest, in the order that gives you the most benefit. Your core, head, hands, and feet are the priorities. Here is how each layer contributes, and when it's worth adding.

A thermal rash vest is the single most effective layer you can add under a wetsuit. Worn against the skin under your suit, it adds a layer of insulation across the core, which is where the majority of your body heat is lost. Thermal rash vests are made from insulating materials, often with a brushed or fleece-lined interior, that trap heat close to the body and hold it there even as cold water flushes through the suit. For the full range of cold water suits these layers pair with, see the full wetsuit range.

The insulation is the primary benefit, but not the only one. A rash vest also prevents the chafing and skin irritation that a wetsuit causes at the neck, shoulders, and underarms during repeated movement. The quick-drying construction means it doesn't hold cold water against your skin between sessions.

Some thermal rash vests include UV protection, which matters for long sessions where your shoulders and upper back are near the surface. If you're layering for both warmth and sun exposure, look for a vest that states its UPF rating.

Thermal wetsuit shorts insulate the lower body: the thighs, hips, and seat. These are large-surface-area regions that lose heat quickly in cold water, and they're often overlooked because the focus tends to go to the core and extremities first. Worn under your wetsuit, thermal shorts close that gap.

Most thermal shorts are made from thin neoprene or a similar insulating material, cut to sit flat under a wetsuit without bunching. The fit needs to be snug: a loose layer traps a thick pocket of water that your body then has to heat, which works against you. A close fit keeps the insulating layer thin and effective.

There's a secondary benefit worth noting. A snug thermal short reduces the water movement between your skin and the suit, which cuts down on the flushing that makes you feel cold every time you duck under or change position. Less flushing means more stable warmth across the whole session.

The head loses heat faster than almost any other part of the body, and it's the area most people under-protect. In water below 12°C, a wetsuit hood is often the difference between a full session and cutting it short, regardless of how well the rest of your body is layered.

A wetsuit hood covers the head and neck and can be worn on its own or tucked under the collar of your suit for a better seal. Neoprene hoods provide insulation directly, and they also protect the ears from the cold water flow that causes surfer's ear over years of exposure, a genuine long-term concern for regular cold water surfers and swimmers.

A hood also cuts wind chill on the paddle out and reduces heat loss while you wait between waves or sets. If your sessions involve significant time with your head exposed to cold air as well as cold water, the hood earns its place quickly. The National Center for Cold Water Safety provides useful guidance on cold water exposure and the physiological effects of heat loss.

Cold feet end sessions. Once your feet go numb, your balance, your board control, and your willingness to stay in the water all deteriorate quickly. Wetsuit boots insulate and protect the feet, and they're one of the highest-value additions for anyone surfing or diving in cold water.

Neoprene boots come in a range of thicknesses matched to water temperature: thinner boots (3mm) for cool water, thicker boots (5mm and up, often with a split toe or round toe design) for genuinely cold conditions. Match the thickness to your conditions the same way you would match your suit.

Boots do more than insulate. The soles provide grip on the surfaces you cross to reach the water: rocks, reef, slippery ramps, and boat decks. That traction reduces the risk of a fall on a sharp or unstable entry, which is a real consideration on many cold water breaks where the entry is over rock rather than sand.

Hands are the last priority to cover but the first to feel the cold, because they're small, constantly moving, and always exposed. For cold water diving and winter surfing, wetsuit gloves keep your hands functional: warm enough to maintain grip, dexterity, and the ability to do what the activity requires.

Gloves come in different thicknesses, and there's a genuine trade-off to understand. Thicker gloves are warmer but reduce dexterity and feel; thinner gloves preserve dexterity but offer less insulation. For surfing, most people choose the thinnest glove that keeps their hands functional, preserving board feel. For diving, where dexterity demands are different, a thicker glove is often the better choice.

Look for gloves with reinforcement at the palms and fingertips. These high-wear areas fail first, and reinforcement meaningfully extends the life of the glove, particularly if you're handling a board, a rope, or dive equipment regularly.

Summer layering is a different problem. In warm water, the goal shifts from insulation to comfort, chafing prevention, and sun protection. You're not trying to add warmth. You're trying to make the suit comfortable to wear and easy to get in and out of.

Under a summer wetsuit or springsuit, the right base layer is swimwear made from a comfortable, quick-drying synthetic. Nylon and polyester swimwear work well because they hold their shape, dry fast, and don't chafe under neoprene. A well-fitting one-piece swimsuit is the cleanest option under a wetsuit, with no ties or clasps to create pressure points under the suit.

Fit is the main consideration. Swimwear worn under a wetsuit needs to sit flat and stay in place. Anything that shifts, rides up, or bunches under the suit becomes an irritation you can't fix without taking the whole suit off. A snug, smooth fit is what you're after, with straps that don't dig in under the pressure of the neoprene over them.

Style is a matter of preference and activity. A one-piece gives the smoothest layer under a suit. A bikini gives more flexibility if you want to remove the suit and stay in your swimwear for time out of the water. For open water swimming specifically, a performance one-piece under a springsuit is the combination most swimmers settle on.

A rash vest earns its place in summer for reasons that have nothing to do with warmth. Worn under a wetsuit in warm conditions, a rash vest prevents the chafing and skin irritation that neoprene causes at the neck, underarms, and shoulders during repeated movement. Anyone who has finished a long summer session with a raw neck from their suit understands the value immediately.

Rash vests are made from lightweight, quick-drying material that stays comfortable in warm conditions rather than adding heat. They come in short-sleeved, long-sleeved, and sleeveless cuts, so you can match the coverage to how much sun protection and chafe protection you want.

Sun protection is the other summer benefit. A rash vest with a UPF 50+ rating shields the shoulders and upper back, which are the areas most exposed to the sun during any surface water activity. For a full breakdown of suit types and how they pair with base layers across the seasons, see the women's wetsuit guide.

A practical reference for matching your layering system to the conditions:

• Below 10°C: Full layering system. A 4/3mm or 5/4mm wetsuit with a thermal rash vest, hood, boots, and gloves. All five layers earn their place at this temperature. This is serious cold water and under-layering will end sessions fast.
  
  
• 10–14°C: A 3/2mm or 4/3mm wetsuit with a thermal rash vest and boots as the priority additions. Add a hood for sessions over an hour or in windy conditions. Gloves for anyone whose hands run cold.
  
  
• 14–17°C: A 3/2mm wetsuit or springsuit with a thermal rash vest for longer sessions. Boots optional depending on entry and personal cold tolerance. Most people don't need a hood or gloves in this range.
  
  
• 17–20°C: A springsuit with swimwear underneath. A rash vest for chafe and sun protection rather than warmth. No cold water layers needed.
  
  
• 20°C and above: A springsuit or no suit at all, with swimwear or a rash vest underneath for comfort and sun protection. Layering here is about chafe prevention and UV, not warmth.