Hydro-lysis (water-breakdown), as the name indicates, is the process in which water molecule is used to breakdown the other larger molecules into smaller ones with the release in energy.
There are hundreds and thousands of reactions occurring in living body that need the support of water for the breakdown of large molecules (polymers) like carbohydrates, proteins and fats into smaller units to release the energy.
There are many enzymatic reactions in which water holds key position to liberate the energy. For example, there is a family of enzymes called hydrolyase, which use the water molecules for their proper function. They break the bonds of many molecules like cellulose, for every one bond of cellulose that is broken, one water molecule is needed.
Another example, is the breakdown of ATP. As, we all need energy for our survival in the form of energy packets called ATP (Adenosine diphosphate). Now, the energy can only be provided by ATP when it is broken (hydrolyzed) by 2 molecules of water to form ADP (Adenosine diphosphate) with the release of 7,000 calories of energy per mole. You can see the reaction in figure.
Hope it helps! :)
