The use of floats on hook traces seems to be largely a Hawkes Bay thing. It started with plastic bubbles in an effort to lift baits off the bottom and away from pesky paddle crabs. Now it has evolved into an art form using bright coloured, uv coloured, fluorescent and luminescent floats. These days it is more about activating the bait to attract fish. It is well documented that a moving bait attracts fish so floats big enough to get a bait moving in the surge are used and colours and other finishes are used to attract attention to the baits.