Someone I know is racing this weekend in supposedly 52 deg F waters off of Pt Magu. Any suggestions concerning: ear plugs, pre-race warmup, wet suit hood, etc? She’s from Hawaii so there may be some thermal shock involved.
Lots of bodyfat and keep your leg hair.
Get two baracuda caps for her head. It helps a lot. I swam many winters in SF bay without a wetsuit and the secret is to keep your head warm.
I make sure I get my core temp up on dry land first, a little biking and then running. Second, get into the water slowly, i.e. aclimatize and swim a bit to get the body temp back up after the initial shock has lessened. Definitely don’t wait for the race to start and just “jump in”.