Angling - Mini Bubble Floats

[Captain Spod]

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. (Also submitted in main Sport section)

[Toureman]

perhaps they would float if you put air in instead of water?

[boxtops]

You want to ask this when DocSpock is on here, he said he was going fishing today so probably not back yet!