Open mouth with no air, push air out in succession with your tongue from your lungs, the first bubble done right will expand and thus slowing down while getting wider, the second bubble blown with less air will rise faster in a smaller tighter group, going through the first, as it spreads it slows down to let the first catch up, i have seen it done in person on a trip in cancun, the dolphin swim instructor there george (maybe) does it...

This was not explained to me by him, but seems theoritically possible.