- What are you paddling?
- Do you paddle alone?
- What are your skills: Can you roll, brace? How fast can you re-enter you SINK and or scamper back onto your SOT?
For example, when I surf in the winter, the water temps do get to 40 and below. I am on a waveski, exposed to the water and air constantly but am not in the water all the time like a board surfer. I do a lot of intermittent sprinting and do get hot. But I can roll to cool off. Generally I am okay for several hours, non-stop, in my waveski with a 5/4/3 wetsuit. However, if I were in SINK and can’t roll, I would probably overheat if I did anything more than lily-dip.
In a SINK, I probably would go down to a 4/3 wetsuit which can give me a good 15-20 minutes of immersion in 40 and below water, allowing plenty of time to re-enter or re-mount on my own. But, I can still roll to cool off. Frankly in the same water temp, I am willing to go down to a 3/2, with a drytop over that (as opposed to a hydroskin underneath which would be too binding if your 3/2 fits snugly as it should. The 3/2 is not recommended unless you have good skills and/or partners with assisted rescue skills.
If you can’t roll, I would say go with a 4/3 and with the option of a drytop over it if air temp is nearing freezing with wind. Again, I assume you are paddling with a partner skilled in assisted rescue.