This is a fishing bobber that I have designed for the Make It Float Challenge. It has taken many revisions to get a model that I'm happy with. My major revisions for the bobber and lock are shown with earliest revs on the left and finished revisions further to the right. Although all of the bobbers and locks worked, my revisions were aimed at becoming lighter, stronger and easier to print.
Incorporating the extrusion in the bobber to other hollow models it is likely that you could make almost anything into a Bobber with the same locking mechanism.
After printing the Bobber and its Lock you only have to insert the lock until it clicks into the bobber. At this point the lock can't be removed, this design keeps you from dropping and losing the lock. That is the only step needed to assemble the bobber. To attach it to fishing line you just have to place the line in the notch located between the two arms or the lock and push the lock until it clicks again. To release the lock, simply squeeze the two arms and pull the lock out.