Every freediver is different when it comes to how quickly they lose heat and start to feel cold in the water. You can use the temperatures and wetsuit thicknesses below as a general recommendation for a 1-hour freediving session:
28°C (82°F) and warmer: 1 - 1.5mm
24 - 28°C (75 - 82°F): 3mm
18 - 24°C (64 - 75°F): 5mm
16 - 17°C (61 - 63°F) and colder: 7mm
Get cold easily?
If you feel chilly quicker than others in the water, choose a wetsuit thickness based on the higher temperature in each of the ranges above. Consider purchasing a wetsuit with an open cell interior, which clings to your skin and minimizes water circulation, keeping you warmer longer. Important note: Open cell wetsuits must be put on in water or with lubricant.
For your time out of the water wearing a wet wetsuit, note that wetsuits with a fabric-lined exterior will feel cooler in windy weather as water evaporates from its surface.