I don't sail much, but have sailed on a couple of trips on a friend's boat - 2 weeks around Inner Hebrides / Northern Ireland / Isle of Man / Liverpool on one trip; 3 days Hayling Island to Liverpool on another. Sure, night watches, sea sickness etc are a bit of a challenge, but not too bad on basal bolus insulin regime.
Husband and I pleasure sail in Solent on small yacht. I always test regularly carry jellybabies for an emergency and find it such a relaxing passtime that surely helps my control. Not sure how I would cope with hard core but as long as you are not missing snacks, if required and having some form of carbs can't see any reason why knot??