Lake Profondo has a depth of 84 feet. Lake Segundo is 5/6 as deep. What is the elevation at the bottom of Lake Segundo (Remember, the elevation is below sea level. Account for this in your answer.)
Lake Segundo is 5/6 * 84 feet = <<5/6*84=70>>70 feet deep.
Since the elevation at the bottom of Lake Segundo is below sea level, the elevation at the bottom of Lake Segundo is -70 feet. Answer: \boxed{-70}.
To find the depth of Lake Segundo, we need to multiply the depth of Lake Profondo by 5/6.
Depth of Lake Segundo = Depth of Lake Profondo * 5/6
Depth of Lake Segundo = 84 feet * 5/6
Depth of Lake Segundo = 70 feet
Since the elevation at the bottom of a lake is below sea level, the elevation at the bottom of Lake Segundo would be -70 feet.