It's hard to decide what exposure suit to wear. Here's a guide to help in the process, which I'll walk you through using.
To begin, find out the temperature range for the water you'll be diving in. Let's pretend I'll be diving in water that is 72-75 degrees fahrenheit. Next, we'll modify this range based on several factors:
- Depth - Deeper water tends to be colder, so if this is a deep dive (around 30m / 100 ft), consider subtracting about 5 degrees from your temperature range. In my example, I'll be diving normal depths around 20m / 60ft, so the range remains 72-75F.
- Duration - What's your air consumption like? If you tend to dive for over 45 minutes, subtract 5 degrees from the range. My dives will be around 45 minutes, so again, no change.
- Number of dives - Repetitive, multi-day diving needs to be taken into account. If you will be doing this kind of diving, subtract another 5 degrees. Let's say I'm diving for a week, so my range now becomes 67-70F.
- Female - Women generally get colder than men, so if you're female, subtract 5 degrees. I'm a man, so no change needed.
- Personal experience - What kind of diving are you used to? Does cold water not bother you much? Depending on your answer, choose a number from near the bottom or top of the range you currently have. I tolerate cold decently, but by no means am I in the Polar Bear Club. Based on personal preference, I'll use the middle temperature, 70F.
You now have a temperature (in the example, 70F). Plug this into the following table to get a recommended exposure suit. If you find yourself where two ranges meet and aren't sure what to do, err on the side of too much exposure suit.
[Click to enlarge]
For our example temperature of 70F, I have the option of a 5mm fullsuit, a 7mm fullsuit, or a 7mm fullsuit with hood. I'll be diving quite a bit, so I'll be cautious and dive with a nice, thick 7mm wetsuit. Just for safe measure, I'll pack a hood in case I get cold later in the week.
[Click to enlarge]: http://thedivingblog.com/uploads/2010/03/wetsuit_guide.jpg