To find the depth of Lake Segundo, we can calculate it based on the depth of Ke Profondo, which is 84 feet. Since Lake Segundo is 56 feet as deep as Ke Profondo, we can calculate Lake Segundo's depth as follows:
\[ \text{Depth of Lake Segundo} = \text{Depth of Ke Profondo} - 56 = 84 - 56 = 28 \text{ feet} \]
Since elevations below sea level are represented as negative numbers, we express the depth of Lake Segundo as:
\[ \text{Elevation at the bottom of Lake Segundo} = -28 \text{ feet} \]
Therefore, the elevation at the bottom of Lake Segundo is -28 feet.