Having fishing lodges throughout North America, we have learned a thing or two about netting fish. Throughout our experience we believe the best piece of advice for netting a fish is not something a person should do, but something they should NOT do. And that is to never, ever, sweep from behind the fish trying to net it. It just wont work. The fish, albeit tired, can still swim faster than you can move your net through the water. The bag of the net will experience a lot of resistance when moving it through the current. Instead, when the time is appropriate, try and have the angler get the fish’s head either up out of the water or up in the water column, then have your net underneath it and simply lift up. Fish cannot swim in reverse so if you get the net beneath or in front of the head, you should be able to land it. But no matter the size or species of fish, do not chase it with your net!
More Timeless Tips:
For my two bits the best netters do as you’ve stated…head near the surface, and head first, and then they dip under the fish quickly having a hold of the net bag out of the water. I’ve experienced the netter holding the net with a submerged bag, and just before they move the net under the fish the fish dives, and leaves the hook, or hooks in the net, and gone.