The Alias star has now revealed the stunt was unplanned, and it broke her cell phone which she had in her pocket at the time of the dunking.
Garner tells Access Hollywood, "If you drop your phone, or if your husband tosses you in the pool on the ALS Challenge and you weren't expecting it, and your phone was in your back pocket and it got killed... you have to go a day without your phone!... I had a day without my phone, and at first, it was, 'Ben, you could have told me, so I could have taken it out of my pocket,' but (then) it was so liberating not to have it and not to check it, and just be like, 'Well, people will have to call me if they need me!"'
- WENN