At Trievents #1 I was mentally prepared for the water temperature, but that did not stop my body from exhibiting the classic responses. Mentally I was perfectly calm, and I knew exactly what was happening. However, the more I put my head in the water the shallower my breaths became.
My plan was to keep moving and to keep my head in the water. About half way through the swim I was back into normal form. In retrospect I question if this was the right strategy. I wasted a lot of energy on the first half of the swim and paid for it on the bike.
What is your strategy for dealing with cold-water shock on race day?
I deal with that by getting into the water well before my start time and spend at least 10 minutes in there getting acclimated. I get my face in the water and into my wetsuit then start doing various drills and short swim bursts to get a fast swim start feeling fresh into my mind.
I will use 2 swim caps if the water is in sub to low 60s range. Neoprene cap below 55°F.