What is the volume of 25 ml of water?

The volume of $25 \cdot m L$ of water is $25 \cdot m L$.
Or $0.025 \cdot L$. Possibly, you meant to ask the mass of $25 \cdot m L$ of water. Since the density of water, $\rho$, $=$ $1.0 \cdot g \cdot m {L}^{-} 1$, the $\text{mass"=rhoxx"volume}$ $=$ $1.0 \cdot g \cdot \cancel{m {L}^{-} 1} \times 25 \cdot \cancel{m L}$ $=$ $25 \cdot g$.
You already gave it to us. If you meant in ${\text{cm}}^{3}$, ${\text{1 mL" = "1 cm}}^{3}$. Thus, ${\text{25 mL" = "25 cm}}^{3}$, though $\text{mL}$ is already a unit of volume.