The Ocean Hunter Speed Needle is used to thread your fish onto your floatline. It is one of the fastest and easiest ways for stringing fish. Every gun should have a float line attached to their handle which should be attached to a float, the aim of the speed needle is to minimize the effort after catching a fish.
Once you have catch the fish, unclip the speed needle from your gun, thread it through the fish mouth and out through its gill, then clip the speed needle back on. As you swim off to start looking for your next target, the fish you have just placed on to your float line will be taken by the current up the line to the float.
Its extremely simple yet saves alot of time.