When Ben surfaces in the Enchanted Lake, his mind finally quiets in a way it hasn't since he ate Mal's cookie. He presses his back to the cliff wall, out of sight of the gazebo where Mal is sitting, and forces himself to think, to ignore the lingering voice screaming that he needs to make Mal happy, that he needs to show his love for her, that he can't be without her.
He ducks his head underwater again.
The voice is quieter still when he surfaces, and he goes under a third time to make sure it's truly gone. Three is a magic number— three fairies for Aurora, three wishes for Aladdin, three nights at a ball for Cinderella.
If he reveals that he was spelled, it will call into question his capability to rule— there's already talk that he's too young. If the fact that his first order resulted in his safety and free will being compromised, it will be the end of his campaign to be rid of the Isle.
But him falling in love with Mal, the girl from the Isle, will make a perfect story to build public goodwill. If Mal is willing.
She's been obsessed with the wand, just like her friends. She wants it for something, and she definitely wants the barrier gone. The wand is the fastest and safest way to remove the barrier, and the easiest way to get close is the coronation.
She still drugged him, basically. He can't trust her, not yet.
There's a splash, Mal's voice calling his name.
There's more splashing. Ben edges closer to the gazebo, staying out of sight, until the splashing turns to flailing, Mal's voice disappearing.
Whatever her reasons, he can't let her drown. That would be even worse PR than her spelling him.