This post is for my Greek chef friends who produce kilos of calamari for tourists. Deep frying works by heat transfer of the convecting fluids (oil) and buoyancy between hot and cold layers of the food and is divided into three stages: the settling period, the constant-rate period, and the falling rate period.
A good strategy which works well is to coat the food in a wet batter so it acts like an insulating barrier. The coating helps develop a superb crust as it protects the food from overcooking. The water in the batter boils steadily with a pocket of cooler humid air between the batter and the food.
The food essentially bakes in this cool zone of moist air rather than frying in the oil. The thickness of the batter determines just how cool the food stays wetter batters cool food more.