The photo shows Ace, 14 months, laughing while suspended several feet above Johnson's head, presumably after being thrown into the air by his dad, who stands below him in the water, waiting to safely catch him.
"I was on a plane to NYC today and I missed out on this!!!" Simpson, 34, captioned the playful snapshot. "I'm in LOVE with the 2 of them. #boyswillbeboys"
Simpson recently raved about her husband to Access Hollywood, saying her kids can't get enough of him. "Ace is obsessed with his dad, Maxwell is obsessed with her dad," she said. "I think it's because he can lift both of them [at the same time]. Eric is the best."
She added that she feels "sexier" now that they're married. (They tied the knot in July after a four-year engagement.) "Being married, for me, it defines so much more than even having kids. We still feel like we're on a honeymoon," she gushed. "I feel sexier as a wife and a mom."