You dont need a 3 way swivel. You tie a drop shot hook (Octopus hooks) to the line using a Palomar knot and leave the tag end of the line about 1-2ft long. Then tie a weight to the tag end the length you need. Be sure to use an overhand knot to the weight so it breaks off easily if snagged, that way you don't lose your whole set up.

It really sounds more complicated than it is. Actually its quite simple once you see it and easy one you've used it. Check out that web page, there lots of info and suggestions there.