I don't know what the average might be, but it often takes a long time to retrieve the fish. The first job is just to follow the reel line or float line under the kelp to find the fish. I have a 120 foot float line and I might have to dive several times, following the line under and around kelp, coming up for air, and then continuing. I've seen cases where the fish went under kelp at 50 feet, came back up near the surface, went back down again, etc. If the visibility is poor (and it often is) you can't see the line and take shortcuts- you have to follow every foot of it.
Then when we do find the fish, we usually have to cut kelp. The fish has often wrapped the shooting line around a bunch of kelp and is buried deep in the mess. In poor visibility, we have to be very careful to avoid being tangled, and to make sure we are cutting kelp instead of shooting line. It may take several dives. Often we end up unclipping the shooting line from the reel line or float line, and sometimes even cutting the shooting line from the shaft, bringing the fish up, and then pulling the reel line or float line up from the other end.
Regarding float lines- its impossible to use a float that provides any buoyancy to fight the fish. While hunting it would be impossible to drag it down through the kelp. Many people use a naked line with nothing on the rear end. I use a small float that simply serves as something to grab if all the line has been pulled through my hand. It slides through the kelp easily and makes it easier to find the end of the line.
Most people use breakaway float lines rather than attaching the line to the butt of the gun. If the line is attached to the gun, then the gun gets pulled through the kelp and might hang up and cause the fish to tear off. And even if that doesn't happen, it complicates retrieval. You have to cut a fish out of the kelp, and then go cut a gun out of the kelp.
