Water ovens are used for sous vide cooking. In this style of cooking, food is placed in a vacuum-sealed bag and immersed in a water bath. The water is heated to the same temperature at which the food is considered cooked, for example 125 degrees Fahrenheit for salmon.
High-end restaurants have used sous vide cooking for decades. Sous vide cooking is useful for foods that can easily dry out or overcook and need tenderizing. Seasoning or sauces can be included in the vacuum bag during cooking, or the food can be seared and sauces added after the food is removed from the water oven.
The food is not placed in the water oven until the water is the correct temperature. A review in the November/December issue of Cooks Illustrated noted that it took almost an hour to bring the water up to the temperature for hard-cooked eggs in a 2.3-gallon water oven.
Sous vide cooking can also be accomplished using stick-style machines that are less expensive and bulky than water ovens. The Cooks Illustrated review recommended the sticks, noting that they heat the water faster than the ovens. However, there is more risk of water evaporation using the stick-style machines.