Lifeguards responded to a diver who was more than an hour overdue off the coast of Point Loma.
They received the call around 5:30 p.m. to a spot about 1.5 miles off the coast when the diver was late in resurfacing.
The was transported to Mission Bay lifeguard headquarters and was later pronounced dead at UCSD medical center.
The man has been identified as Joel Millecan was diving for urchin at the bottom of the ocean using a hookah line instead of a tank.
The line connects to a compressor and provides an air supply to the diver from the surface.
The person watching the surface of the water from a commercial boat called 911 after bubbles disappeared more than an hour into the dive.
Lifeguards said there is a 65-foot bottom with a lot of kelp and rocky reefs in the area.