Four Leaved Clover
Move to the yellow "X". As soon as the tentacles have retracted, run along the yellow path without stopping. All boxes are now in a position to be moved into the current (green arrow). Start with the top-right box and work back from there.
Once a box is pushed into the current, follow it to build a bridge at the red "X"s. Make sure to collect the Bonus Bubble before bringing the next box, or your progress will be halted.