Sending Unit Float Question

Thanks, Demon. I kind of figured fluid in the float is bad, but I just wasn't sure how it got in there in the first place. No visible leaks along the seam. Is the plastic somehow porous, perhaps? I haven't been able to find just a float by itself from a local auto shop, only the entire sending unit. I'll check online. If i do decide to reseal the existing float, I will have to poke a hole in it, then drain the fluid and reseal it. Now, what could I use to seal the hole?