Answer:
Final position of scuba diver = 7 feet below the surface.
Explanation;
Let us take down direction as positive and up direction as negative.
A scuba diver dives down 15 feet into the ocean, position of scuba diver = +15 feet.
He then swims 8 feet back up towards the surface, position of scuba diver = -8 feet
Overall position = 15 - 8 = 7 feet.
So final position of scuba diver = 7 feet below the surface.