To balance the equation for the combustion of ethanol (C2H5OH) in the presence of water (H2O), we need to ensure that the number of atoms of each element is the same on both sides of the equation. Here's the balanced equation:

C2H5OH + 3O2 → 2CO2 + 3H2O

In this equation, we have:

- 2 carbon atoms on the left side (in C2H5OH) and 2 carbon atoms on the right side (in 2CO2).

- 6 hydrogen atoms on the left side (in C2H5OH and H2O) and 6 hydrogen atoms on the right side (in 3H2O).

- 1 oxygen atom on the left side (in H2O) and 7 oxygen atoms on the right side (in 3O2 and 2CO2).

Therefore, the equation is balanced with respect to all elements.