I made some years ago. Now I find it just as easy to buy them.
Not really hard to make if you can do a haywire twist. If I remember correctly I would use twelve foot of wire. I would cut that in half and put a swivel in between. A hook was attached to the business end and the other end would be attached to a swivel coming off the main line off the reel which I would double up with a spider or bimini hitch. All connections of the wire would be with a haywire twist.
The two six foot sections would work better that a straight twelve foot length. If one length got a kink in it you would only have to change that section out. When you cut the hook off to release a shark you would then only have to replace that six foot section and you were back in business again.