The decision whether to wear a wetsuit in a triathlon, or any open water swim, based on water temperature is very personal. Some triathletes get cold easily, while other athletes find themselves prone to overheating. Also, some athletes enjoy the added security of a wetsuit in open water.
With that being said, there are general guidelines that can be a helpful guide, especially for new triathletes.
Under 53°F (11.5°C)
Very cold water that is generally considered too cold to swim in. If you are going to be swimming in water this cold you are going to want a thermal lined wetsuit, such as the soon to be released Ocean 1.0 wetsuit, as well as a thermal cap or hooded vest, neoprene gloves, and booties.
53°F to 61°F (11.5°C to 16.1°C)
The water is cold, but swimmable for most triathletes. If you are regularly swimming in water this cold we would recommend the Flōh 1.0 wetsuit. The 1.5mm arms will provide additional warmth while still allowing for full mobility. If you find yourself getting cold at this temperature you can try to double layer your swim cap, use a neoprene swim cap, neoprene gloves, or booties.
62°F to 76°F (16.2°C to 24.4°C)
This is prime wetsuit temperature. The water may feel cool when you first get in, but once you begin to swim most athletes will find swimming in a wetsuit to be very comfortable. We would recommend a Fjord 1.0 wetsuit for most athletes regularly swimming in this range of water temperatures.
77°F to 83°F (24.5°C to 28.3°C)
Most athletes will find the water is too warm to swim in a wetsuit. You may find yourself feeling sluggish and overheating in a wetsuit. If you are keen to wear a wetsuit we would recommend the Fjord 1.1. The sleeveless Fjord 1.1 will keep your body temperature slightly cooler. Many races will not allow wetsuits to be worn, or if a wetsuit is worn, those athletes may be ineligible for awards. In these circumstances we would recommend our Tsunami 1.0 Speed Suit.
Over 83°F (28.3°C)
Virtually all athletes will find the water temperature too warm to wear a wetsuit. Wearing a wetsuit at this water temperature can cause premature fatigue and overheating.
You will be faster swimming in a wetsuit than not. deboer wetsuits use WhaleSkin neoprene throughout the body, which has 4-way stretch, a feature unique to deboer. (Traditional neoprene is 2-way stretch, which means it only pulls in one direction) This means that you don't feel like you are fighting your wetsuit that you experience with other brands.
If you have any questions about any deboer product feel free to email us at firstname.lastname@example.org.