Answer: The diver descended 20 meters below sea level and then ascended 8 meters.
Step-by-step explanation: The expression 2 + (-20) + 8 describes the diver's movements in relation to sea level. The first number, 2, represents the diver's initial position at sea level. The second number, -20, represents the diver's descent below sea level by 20 meters. The third number, 8, represents the diver's ascent back up to sea level. This can be interpreted as the diver starting at sea level, descending 20 meters below sea level, and then ascending 8 meters back up to sea level.