Another question on Bernoulli's principle

Yes it can, but the form of the balloon (which resembles that of an egg - one side is nearly spherical, the other is more elongated) is imo such that it sits on the side which allows water to wash smoothly over it's curved surface, with no separation and hence with maximum suction.

 

... as opposed to those with a form which resemble that of A. Eckberg ...

(It must have been the fact that the balloon was black that made me think of this)

Silvia, La Dolce Vita, Trevi Fountain, for those who haven't seen the film.

 

How to float a ping pong ball on air - The Coandă Effect

 

Anita and her unsteady balloonns in a fountain... another D'Alembert paradox