Super easy to print with no supports. Its printed in two identical halves that are glued together. The glue bond does not need to be watertight since the halves float as they are! Works well as it is but if you want to enhance the look you can wrap some rope around it as in the first picture. Can be scaled up in the slicer to match your keys' weight. Inspiration from the store bought ones made from cork or ones made from rope completely. However this should be more visible when printed in bright colors or if using bright colored rope.

The cover picture is from https://www.etsy.com/listing/985199526/cork-floating-keychain-two-tone-35 where you can buy premade ones from CordialKnots!