The sinking boat I assisted was half a mile from the entrance to my marina. Seems like boats are less likely to have dingies, EPIRB's, etc. for a day sail, yet the water temp is still in the 50's in the SF Bay.
My rationale is weak, but I am speaking of the warmer water, shallow, slow moving St. Johns River south of Jacksonville, Florida that is three miles wide at the most and a vary calm play place. I will reconsider my habit due to these postings.