Saw a pack of four in a 99p shop and couldn't resist buying them. I've tried to find out how to use them and although I've spotted that they've got stoppered holes for filling with water, I have to wonder why you'd make a float, well, sink? Any ideas out there? Thanks.
Adding various quantities of water will make the float more, or less, sensitive. The more water you put in the less tip of the float will show above the water making bites easier to detect.