is that like an object floating underwater that has water acting against it but has buoyancy acting to make it rise so that it's stationary but there's still a force trying to make it accelerate?

No, in that case the forces would balance so that the acceleration would be zero. The point with the ball is that its velocity is changing, even when it is instantaneously at rest at the top of its motion.

If the ball were sitting at rest on the earth, however, then its acceleration would be zero. Even though gravity pulls down on it, there's a corresponding upward force exerted by the ground that balances it out.

Being "at rest" (i.e., zero velocity) with nonzero acceleration only happens instantaneously.

But the air pressure on anything is still acting against anything sitting still so is still an active force, no? Like if all the air on earth suddenly disappeared everything on earth resting would "pop up"?

PS

Are you going to tell him the newtons equal out in that case?

Huh?

Air pressure adds weight.

I mean that the air pressure is adding permanent change to velocity that if removed would stop changing velocity. Like what's the difference between a ball hanging in midair and a ball sitting on the ground with air pushing down on it when if that air were removed would change/add velocity?

The forces on the ball hanging in midair aren't balanced. That's why it is only instantaneously at rest.
I think I'm interpreting your question right?

That makes sense, I think.

Basically at the peak the ball is already set to move back towards the earth. So even though for an instant it isn't moving it will have a non zero velocity because at any given moment later it will have moved?

Is there a describable difference between balanced and not balanced though?