I have been trying to incorporate local woods into my corn cob floats. I have cedar and spalted ash I cut down for knife handles. I used my table saw to rip these into 1/4 in square sticks. I just pushed the stick through the pith of a piece of cob and glued them into place. I then shaped the ends with the belt sander. Tied on the eye and they are ready to seal.
I use Min Wax clear polyurethane because that's what I had on hand when I started making floats. It seems to hold up well so I kept using it.. The float in the pic stayed afloat for 20 straight days with enough weight to keep it upright.
These floats are made of Oak and Birch scraps from a cabinet shop ( free ) and Brazilian Walnut from a friend who installs hardwood floors ( also free ). It doesn't take a big piece of wood to make a float and these small pieces are usually discarded. These are ready for the eyes and finish.