Cold weather is coming. A turnover in winter can be painful, deadly or
just a "thing" if you are prepared. most body heat is lost from the
head. Heres a page on caps for cold water kayakers or windsurfers. A
warm head covering is cheap insurance combined with a floatation
device (pfd)and a plan to reenter.

http://www.geocities.com/lapswimr/kayakcaps.html