How do I create a physics sprite that defies gravity?

I have a jumping game that uses objects with physics and gravity.

I'd like to have some objects - helium balloons - that float or hover in the air, yet also have physics properties - such as the player pushing them out of the way.

Does anyone know how I can create these kinds of sprites - with physics, but defying gravity?

Every time I try to make this kind of object, it always immediately falls to the ground.

Thanks!

I am not sure at all it'll work, but:

you can try to set an acceleration upards, the same value as the gravity, when the object is created (It should stop the falling), then add a velocity upwards too

As Aphrodite says

every tick - Balloon apply physics force (0,-gravity) at image point 0

But also make sure to:

set balloon density to 0

set balloon damping (both) to a high number (0.9 ?)

Thanks to both of you - worked great!