So Dad enters the rough water before his buddy. He waits for his buddy. His buddy enters the water and does not see dad. Buddy decides to descend without dad and to look for him. Then he looks for him underwater for a minute and then resurfaces and immediately indicates that he has lost his buddy... Then dad is found floating 1000 feet behind the dive boat and is tired and they drag him back to the boat, where he collapses and dies.... Is that the story?
Was the dive boat tied to a mooring bouy? Where they diving a wreck? Did dad have a whistle or dive alert (air powered horn)? What did dad's dive computer show? Did he go underwater to any depth or did he stay on the surface?
If dad did not descend, but instead, got over exerted on the surface how and why did he get so far behind the boat? Would he not call for help, blow a whistle, yell to the crew and why would the crew not notice a diver on the surface drifting back behind the boat and allow him to get nearly 1/4 mile behind the boat before sending a swimmer after him?
If that is the story, it is hard to understand how his buddy left him, went down to look for him, couldn't find him and then resurfaced all in 60 seconds? That would seem to be a very short time to accomplish all those things, but it would depend on the depth and water clarity, I assume. If dad started to drift backwards right before the buddy entered and then the buddy dove only for one minute and sounded the alarm, how would dad get so far behind the boat?
I would ask the buddy, how deep did he dive in his search for dad. That would give some indication of how long it took and an indication of how long it took to sound the alarm.
Even though a diver can comfortably rest on the surface by inflating their vest, if they were in rough water and there was a strong current, and they were trying to descend down a mooring, then a diver would need to swim hard to fight the current at the surface if he chose to (or was directed to) wait for his buddy at the surface near the mooring buoy. It might be difficult to hold onto a mooring buoy in over 4 ft seas in a strong current at the surface, especially if a dive boat was using it. So it is conceivable that someone might chose to try to hold position and kick against the surface and wait for buddy on the surface. This could be very strenuous.