While there are other important components, like proteins, carbohydrates, lipids (fats), and nucleic acids (DNA and RNA), water makes up the majority of the mass of most living organisms. Here's a breakdown:

* Water: Typically accounts for 60-70% of a cell's mass. It acts as a solvent, allowing chemical reactions to occur, and also helps with transporting nutrients and waste.

* Proteins: These are the building blocks of cells, acting as enzymes, hormones, and structural components.

* Carbohydrates: These are energy sources and provide structural support.

* Lipids: These are fats and oils, acting as energy stores, insulation, and cell membrane components.

* Nucleic acids: These are the blueprints for life, carrying genetic information.

So, while other elements are crucial, water is the most abundant and essential component of living matter.