I wouldn't rush hoe to deal with this, but I would drain the water out. You could probably get away with just a heat source under the engine cover, but it is simple enough to drain it down. Definitely no need to use the antifreeze. Pay attention to get the water out of shower or heater is you have either.
CUSTOM WHEEL & TIRE PACKAGES
$125 LED LIGHT PACKAGE - FREE SHIPPING
REBUILDING HOLLEY MARINE CARBS - $249 DELIVERED
REBUILT COMPLETE MARINE HOLLEY 4160 CARBS
FOR 302, 351 & 454 STARTING AT $425
Email - email@example.com