Arctic Undersuit

Hugh Miller

Award Winning Filmmaker

Thermocline - Neutrally Buoyant Wetsuit

The Thermocline neutrally buoyant system represents an evolution in thermal protection, using state of the art materials to maximise performance without compromising on comfort. The Thermocline neutrally buoyant wetsuit system comprises the long sleeved top and the "explorer" giving the equivalent protection to a 3mm wetsuit but weighing less than 1kg (2.2 lbs). Thermocline also provides a real solution for people who suffer from neoprene allergies by eliminating contact between the skin and the wetsuit.

Thermocline Full Suit/One Piece


Thermocline Full Suit/One Piece
Get the thermal performance of a 2mm neoprene suit, without the neoprene. This is the ultimate warm water-wetsuit. Neutrally buoyant, machine washable, breathable, lightweight and hypoallergenic, the Thermocline full suit combines our experience with high technology fabrics and design with our passion for diving to provide a more comfortable and convenient diving experience. The comfort is not limited to the dive however. The breathable fabric ensures that the wearer is more comfortable when fully kitted up and waiting to get into the water. Weighing less than 1kg, the suit is ideal for travelling divers, keen to keep baggage to a minimum. It is fully machine washable so can easily be kept fresh and clean between trips. The suit is neutrally buoyant, allowing less lead to be worn and it dries quickly, even during the surface interval. Available in Men's and Women's styles.

Thermocline Explorer


Thermocline Explorer
Available in both Mens and Womens styles, the neutrally buoyant and breathable. Thermocline Explorer enables diving with the need for little or no lead. Fluctuations in the buoyancy of the suit with depth are not a factor as they are with neoprene, and the suit is more comfortable in warm conditions above the surface.

When paired with the Thermocline long sleeved top, it makes a perfect alternative to a neoprene suit, yet is lighter weight and easier to pack when traveling. On its own, the suit can be worn in warmer water conditions or underneath a neoprene wetsuit to add the thermal equivalent of 2mm of neoprene.

products in the range, Mens






products in the range, Womens






products in the range, Essentials

  • #


  • #


  • #

    Thermocline Socks

Thermocline- Features

Neutrally Buoyant

The Thermocline range is neutrally buoyant, so unlike neoprene wetsuits, it requires no extra lead.


The Explorer wetsuit and the long sleeve top weighs less than 1kg (2.2 lbs), and can be packed down to a very small size, without damaging the suit, making the Thermocline ideal from dive travel.

Hypo-allergenic - A Solution to Neoprene Skin Allergy for Divers

Thermocline garments have been very successful in helping people with neoprene skin allergy to continue to enjoy their diving. The lightweight neutrally buoyant wetsuit system can be used instead of a traditional neoprene wetsuit for warm water diving, or it can be used underneath a neoprene suit to provide an effective barrier to skin contact. Allergic reaction to neoprene is generally ascribed to the accelerants used to manufacture the man-made rubber (i.e., thiurams, carbamates, thioureas, thiazoles). While not life-threatening, if left mismanaged or untreated, these reactions can cause permanent damage to the patient/user's skin. Therefore, an accurate and complete diagnosis is essential and if it occurs, a doctor should be consulted.

The manufacture of the Thermocline range does not involve any of these accelerants and many neoprene skin allergy sufferers have been helped by using Thermocline.

This is taken from the website of Andy McLeod – an underwater cameraman and producer who suffers with neoprene skin allergy.

"After a year of searching the internet, I have found the solution that works for me; a suit from Fourth Element. The suit from the THERMOCLINE range, gives the equivalent thermal protection of 2.5mm of Neoprene. This can act as a barrier thick enough to be able to wear some additional neoprene on top. I ordered the long-johns with long-sleeve vest and have been using them with a standard 5mm neoprene shorty and plan to try a full length neoprene suit when it gets a little colder."

Thermocline- Sizing

Use the table below as a guide to help select the correct size Thermocline. If you require any further assistance/advice please don't hesitate to contact us.

mens size chart

Sizes Height Chest Waist
Inches Cm Inches Cm Inches Cm
Small Short 5'3"-5'5" 160-165 34-38" 86-96 26-28" 66-71
Small 5'5"-5'8" 166-174 34-38" 86-96 26-28" 66-71
Medium Short 5'7"-5'10" 171-179 38-42" 96-106 30-32" 76-81
Medium 5'9"-6'0" 176-183 38-42" 96-106 30-32" 76-81
Large Short 5'8"-5'11" 172-180 42-46" 106-116 34-36" 86-91
Large 511"-6'2" 180-188 42-46" 106-116 34-36" 86-91
X-Large 6'1"-6'4" 185-193 46-50" 116-127 38-40" 96-101.5
XX-Large 6'3"-6'6" 190-198 50-54" 127-137 42-44" 106.5-112
XXX-Large 6'5"-6'8" 195-202 54-58" 137-147 46-48" 117-122

womens size chart

Please note the Womens One Piece only runs up to sizes 18/20.
The Womens Explorer runs up to sizes 16/18.

Sizes Height Chest Waist Hips
Inches Cm Inches Cm Inches Cm Inches Cm
6-8 5'3"-5'6" 160-168 28-30" 71-76 22-24" 56-61 32-34" 81-86
8-10 5'4"-5'7" 162.5-170 31-33" 79-84 24-26" 61-66 34-36" 86-91.5
10-12 5'5"-5'8" 165-173 32-34" 81-86 26-28" 66-71 35-37" 89-94
12-14 5'6"-5'9" 167.5-175 34-36" 86-91.5 28-30" 71-76 36-38" 91.5-96.5
14-16 5'7"-5'10" 170-178 36-38" 91.5-96.5 29-31" 73.5-79 38-40" 96.5-101.5
16-18 5'8"-5'11" 172.5-180 38-40" 96.5-101.5 31-33" 79-84 40-42" 101.5-106.5
18-20 5'8"-5'11" 172.5-180 40-42" 101.5-106.5 33-35" 84-89 42-44" 106.5-112
20-22 5'8" - 5'11" 172.5-180 42-44" 107-112 35-37" 89-94 44-46" 112-117

EU Size Comparison Guide

UK USA France Germany Italy
6-8 4-6 34 32 38
8-10 6-8 36 34 40
10-12 8-10 38 36 42
12-14 10-12 40 38 44
14-16 12-14 42 40 46
16-18 14-16 44 42 48
18-20 16-18 46 44 50
20-22 18-20 48 46 52