There are a couple of balloon powered hovercraft disks out there. The advantages of this one are:

• easy operation: There's a mouth piece that simply screws off, so you can blow up the balloon through it and screw it on again without the hassle of attaching the balloon itself. While breathing in you can close the openings on the mouth piece's side to stop air from escaping. The collar at the balloons opening acts as a seal.
  The mouth piece was inspired by uhltimate's Hovercraft V2.
• option to attach 2, 3, 4 or 6 M12 nuts as weights to increase mass, e.g. for experiments on conservation of momentum
• about 2 minutes of hover time (depending on the balloon)
• the mouth piece is printed in vase mode and only takes 1.1g of filament.

Printing:

• disk: a few more perimeters for collision experiments, otherwise standard, no supports.
• mouth piece: vase mode, 0.6mm (or 0.7mm) extrusion width.
  You can print multiple at once with Output Options→Complete individual objects,
  you can print faster with Filaments→Cooling→Slow down if layer print time is below: ~5s