why water is not suitable.....

The density of oil is lighter than that of water, so it will flow on water. If you use water to put out fire caused by oil, water will sink into oil thus unable to reach the fire. It cannot put out fire and will spread the area of the fire.

Oil is less dense than water, so oil always floats on water. When you pour water into burning oil, the water sinks under the oil and the oil rises to the surface. If you add too much water, everything spills out, and the fire will be spread.

還會使火勢擴散，所以這個滅火方法是不行的。

因為水的密度比油高，水會沈於油下，油會繼續燒，無補於事。

If you put out fire caused by burning oil with water, the oil will float on the surface on the water. The fire can still continue burning.