Essentially, at 77 deg F, hypothermia is not going to be an issue.
77 deg F is 25 deg C, and this chart shows 30 hrs to indefinite for that temperature, even naked:
Survival Time in Hours in Cold Water For colder water, body fat and clothing are big factors - see:
PREDICTED WATER IMMERSION SURVIVAL TIMES FOR ANTI- EXPOSURE ENSEMBLES This seems to be a good site on the topic:
Cold Water Survival