Putting this into a scuba perspective....
Some friends of mine were diving the Spiegel Grove in Key Largo several years ago. They had completed their dives and were tearing down their equipment when one of the staff members on their boat started shouting frantically at another boat. He had seen that one of their divers returning to that boat was in trouble, displaying precisely the signs described in the article. The staff on the other boat was apparently oblivious, probably because they did not see anyone thrashing around and calling for help. Getting no response from them, the staff member of their boat starting calling directly to the struggling diver, who for some reason was not filling his BCD but was struggling along the the surface with ineffective swimming strokes, head and mouth sometimes dipping below water level. When the man finally slipped under water completely, the staff member dived into the water and swam to the spot. He caught up with the rapidly sinking diver at about 20 feet and brought him to the surface. They got him to the boat and began CPR. He revived.
I never heard how the other boat responded when their diver was returned to them for transport to the hospital.