The number line shows the elevation of the bottom of a harbor and the elevation of a fish swimming close to the surface. A vertical number line labeled "Elevation (m)" goes from –12 to 2 by twos. Zero is labeled "sea level." There is a mark at negative 1.5 labeled "–1.5 meters" with an icon of a fish and another mark at negative 10.5 labeled "–10.5 meters bottom

What change in elevation is necessary for the fish to reach the bottom?