Both of them hail from Amsterdam! I imagine the bubble idea might have come out of seeing the ocean cleanup barges in operation - they have the problem of interfering with boat traffic where deployed.
Different province and about an hour's travel south from Amsterdam
I guess the frisian province is 'Amsterdam Lake District', rotterdam is 'Amsterdam Harbour', The Hague is 'Amsterdam Government Plaza', and Delft is just 'Amsterdam - Burials of Royals + that place with the solar boats and cars and the plastic barges dept' :P
NB: I think that "Amsterdam Lake District" thing really is how its marketed from time to time to attempt to distribute tourism more throughout the country. The rest a bit more tongue in cheek.
They are not "from Amsterdam".