Wetsuit thickness choice will vary depending on an individual diver's tolerance to cold or warm water, and acclimation. Here's a rough guide for spearfishermen just getting into open cell wetsuits, looking to spend at least 2-3 hours in the water. Thermoclines (sharp drops in temperature between water layers) will affect wetsuit thickness choice. Keep in mind that these guidelines are for open cell wetsuits which are much warmer than double lined/zippered/scuba wetsuits. A 3mm open cell wetsuit will be a little warmer than a 5mm double lined suit. And much more comfortable to wear being more stretchy and having no interior lining to create friction against the body.
1. Rashguard - 80° F (26° C) and up
2. 1.5mm double lined suit Speardiver Reef 1.5mm Spearfishing Wetsuit - 77° F (25° C) to 80° F (26° C)
3. 3mm open cell suit Speardiver Reef Spearfishing Wetsuit - 71° F (22° C) to 77° F (25° C)
4. 5mm open cell suit Speardiver Pacific Spearfishing Wetsuit - 59° F (15° C) to 71° F (22° C)
5. 7mm open cell suit Speardiver Pacific Spearfishing Wetsuit - 45° F (7° C) to 59° F (15° C)
6. 9mm open cell suit - 33° F (1° C) to 45° F (7° C)