Answer:
300 meters below sea level
Explanation:
Given that the reference plane with respect to each dive is the sea level.
The deepest dive by the man below sea level = 100 meters
The bottlenose dolphin's deepest dive below sea level = 200 meters lower than that of the man.
Since the dolphin dove further than that of the man, it shows that it went deeper than that of the man by 200 meters.
Thus,
The deepest dive ever recorded by the dolphin = 200 + 100
= 300
The deepest dive ever recorded by the dolphin relative to sea level is 300 meters.