Water weighs 8 lbs / gal or 32 Lbs / Ft^3 I would just tie a 32 oz water bottle to my vest in a coozy or put cup holders on top of the foot holders on the hull or on the trap line. when you tack grab some water from the cooler and refil the cup holder. and not worry about the rules. you said it was to make it available to drink when you were trapped out right?