as said, don't ever tie anything to yourself. If you must, let it be with an easy to release clip. Stay away from steel wire. The best thing will be to fix your poll spear to your float, search for "floatlines" there are many.
If just swimming without a gun, I tow my float with one of these in hand:
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I can drop it and my float stays close, or clip it on if I want an easier swim.
