I started off by purchasing a length of 13mm balsa dowel, cost me £3 from Hobbycroft and was enough to make 5no. 7 inch floats.
Following this, I sanded off one end ready for the wire loop (being careful not to let the dog eat it). I could have used a swivel, but these are quite costly so I decided to spend £1.50 on 4m of 1mm brass wire. This was twisted around a thin screwdriver to make the eye.
The balsa is cut to make a float 7 inches long, and sanded off at the other end. I then applied a coat of normal household matt white, followed by some white gloss. The end is the painted either orange or black (both will be needed to suit conditions), and ta da!!
I'll be giving it a go this weekend...