3mm vs 5mm Wetsuit: Which Thickness for Diving?
Thickness is a temperature decision, and diving is colder than the same water feels while swimming because you are still and submerged for an hour. A 3mm shorty suits genuinely warm tropical water; a 5mm full suit covers temperate water and repeat dives. Choose 3mm for warm water single dives; choose 5mm if in doubt, because being cold ends dives and raises risk.
At a glance
| Cressi Fast 5 mm Full Wetsuit | Seaskin 3 mm Shorty Wetsuit | |
|---|---|---|
| Water temperature suited | Temperate and cooler | Warm tropical |
| Coverage | Full arms and legs | Short arms and legs |
| Buoyancy added | More, needs more lead | Less |
| Mobility | Slightly restricted | Free |
| Repeat dives | Much better | You will get cold |
| Sting and scrape protection | Full | Partial |
Choose the Cressi Fast 5 mm Full Wetsuit if…
You dive temperate water, do several dives a day, or feel the cold. Each successive dive starts colder than the last, and a suit that was adequate on dive one is often not on dive three.
Check Cressi Fast 5 mm Full Wetsuit on Amazon
Choose the Seaskin 3 mm Shorty Wetsuit if…
You dive genuinely warm water and value freedom of movement, or you want something light to travel with. Be aware that even in warm seas a full hour at depth cools you more than you expect.
Check Seaskin 3 mm Shorty Wetsuit on Amazon
Related
Comparison based on published manufacturer specifications and the general consensus of owner reports. We have not tested these products side by side. Confirm current specifications and prices before buying. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you.
Deciding on a specific model? We review the Henderson 3mm Thermoprene Pro back zip jumpsuit review and Cressi Fast 5mm wetsuit review in full.
Frequently asked questions
How does wetsuit thickness change my weighting?
Thicker neoprene is more buoyant, so you need more lead, and it compresses at depth which changes buoyancy through the dive. Any change of suit means a new weight check in shallow water before you descend.
Is being cold actually dangerous?
It contributes to risk, yes. Cold impairs judgement and dexterity, increases air consumption and is generally considered a factor in decompression risk. Getting cold is a reason to end a dive, not to tough it out.
Should the suit be tight?
Snug, with no gaps at the neck, wrists or ankles where water flushes through. A wetsuit works by holding a thin layer of water in place; a loose suit constantly replaces that layer and chills you.
How we choose: we compare published manufacturer specifications, published training agency standards, and verified owner reviews across retailers. We do not test gear in person, and every depth rating, cylinder capacity and algorithm name quoted here is the manufacturer's published figure unless we say otherwise, so confirm it on the current spec sheet before you buy. Nothing here is dive instruction, and no calculator output on this site is a dive plan. Scuba diving carries a real risk of decompression sickness, oxygen toxicity, barotrauma and drowning. Dive within the limits of your certification, verify every plan with your own computer, and buy the training before the gear that assumes it.
Logging your own SAC rate and gas plans? The Dive Kit & Air Planning Workbook is the paid version of these pages: 8 printable worksheets you fill in with your own numbers, plus the full PDF, $29.