Answer:
x = 240 feet
Explanation:
It is given that,
The angle of depression is 30 degrees from the bottom of the boat to a deep sea diver at the depth of 120 ft.
We need to find the distance x the diver must swim up to the boat. It can be calculate by applying trigonometry as follows :

So, the distance the diver must swim up to the boat is 240 feet.