If the bird starts 37 feet above the ocean and dives from its position to 7 feet below the ocean, the you just add the two numbers and get its total dive.
To draw it draw a graph that goes past to +37 and past -7, then draw a bar representing the birds dive from +37 to -7. The X axis would be time, and the Y axis is the bird's height relative to the surface of the water.
and 
to be inversely proportional, there must be some constant 
such that
when 
, it follows that
, we have